From e86264ca7b7f4cd51f63aa75802fc31d086bd262 Mon Sep 17 00:00:00 2001
From: lyllyl-bp <ksk910629@naver.com>
Date: Wed, 12 Aug 2026 10:54:00 +0900
Subject: [PATCH] [webview_flutter] Add document-start JavaScript API

Adds addDocumentStartJavaScript to WebViewController and the platform
interface, returning a DocumentStartJavaScript handle that can be used
to stop injecting the script into future document loads.

Implements support on Android and WKWebView, including Android feature
gating and WKWebView re-registration when user scripts are reset.

Throws UnsupportedError on unsupported platforms (including web), and
updates examples, documentation, changelogs, generated bindings, and
tests
---
 .../webview_flutter/CHANGELOG.md              |   6 +
 .../webview_flutter/webview_flutter/README.md |  21 ++
 .../webview_flutter/example/lib/main.dart     |  59 ++++
 .../lib/src/webview_controller.dart           |  40 +++
 .../webview_flutter/lib/webview_flutter.dart  |   1 +
 .../webview_flutter/pubspec.yaml              |   8 +-
 .../test/webview_controller_test.dart         |  40 ++-
 .../test/webview_controller_test.mocks.dart   |  74 +++--
 .../test/webview_widget_test.mocks.dart       |  71 +++--
 .../webview_flutter_android/CHANGELOG.md      |   5 +
 .../webviewflutter/AndroidWebkitLibrary.g.kt  | 122 ++++++++
 .../webviewflutter/ProxyApiRegistrar.java     |   6 +
 .../webviewflutter/ScriptHandlerProxyApi.java |  25 ++
 .../webviewflutter/WebViewProxyApi.java       |  16 +
 .../webviewflutter/ScriptHandlerTest.java     |  23 ++
 .../plugins/webviewflutter/WebViewTest.java   |  25 ++
 .../webview_flutter_test.dart                 |  48 +++
 .../lib/src/android_webkit.g.dart             | 110 +++++++
 .../lib/src/android_webkit_constants.dart     |   5 +
 .../lib/src/android_webview_controller.dart   |  51 ++++
 .../pigeons/android_webkit.dart               |  13 +
 .../webview_flutter_android/pubspec.yaml      |   4 +-
 .../test/android_webview_controller_test.dart |  63 ++++
 ...android_webview_controller_test.mocks.dart | 273 ++++++++++++------
 ...oid_webview_cookie_manager_test.mocks.dart |  33 ++-
 .../webview_android_widget_test.mocks.dart    |  70 +++--
 .../CHANGELOG.md                              |   4 +-
 .../lib/src/platform_webview_controller.dart  |  35 +++
 .../pubspec.yaml                              |   2 +-
 ...tform_document_start_java_script_test.dart |  26 ++
 .../platform_webview_controller_test.dart     |   8 +
 .../webview_flutter_web/CHANGELOG.md          |   4 +-
 .../lib/src/web_webview_controller.dart       |  11 +
 .../webview_flutter_web/pubspec.yaml          |   4 +-
 .../test/web_webview_controller_test.dart     |   9 +
 .../webview_flutter_wkwebview/CHANGELOG.md    |   4 +
 .../webview_flutter_test.dart                 |  48 +++
 .../lib/src/webkit_webview_controller.dart    |  87 +++++-
 .../webview_flutter_wkwebview/pubspec.yaml    |   4 +-
 .../test/webkit_webview_controller_test.dart  | 125 ++++++++
 40 files changed, 1402 insertions(+), 181 deletions(-)
 create mode 100644 packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/ScriptHandlerProxyApi.java
 create mode 100644 packages/webview_flutter/webview_flutter_android/android/src/test/java/io/flutter/plugins/webviewflutter/ScriptHandlerTest.java
 create mode 100644 packages/webview_flutter/webview_flutter_platform_interface/test/platform_document_start_java_script_test.dart

diff --git a/packages/webview_flutter/webview_flutter/CHANGELOG.md b/packages/webview_flutter/webview_flutter/CHANGELOG.md
index bae44ba8f51a..af796ab60073 100644
--- a/packages/webview_flutter/webview_flutter/CHANGELOG.md
+++ b/packages/webview_flutter/webview_flutter/CHANGELOG.md
@@ -1,3 +1,9 @@
+## 4.15.0
+
+* Adds `WebViewController.addDocumentStartJavaScript` for injecting JavaScript
+  that runs at the start of future document loads. It returns a
+  `DocumentStartJavaScriptRegistration` that can be used to stop injecting the JavaScript.
+
 ## 4.14.1
 
 * Adds documentation for `NavigationDelegate` callback parameters.
diff --git a/packages/webview_flutter/webview_flutter/README.md b/packages/webview_flutter/webview_flutter/README.md
index d96e4443b050..cf7f9ed8ade9 100644
--- a/packages/webview_flutter/webview_flutter/README.md
+++ b/packages/webview_flutter/webview_flutter/README.md
@@ -61,6 +61,27 @@ See the Dartdocs for [WebViewController](https://pub.dev/documentation/webview_f
 and [WebViewWidget](https://pub.dev/documentation/webview_flutter/latest/webview_flutter/WebViewWidget-class.html)
 for more details.
 
+### Running JavaScript at document start
+
+`WebViewController.addDocumentStartJavaScript` registers JavaScript that runs at the start of every
+document loaded after the call, before the scripts of the loaded page run:
+
+<?code-excerpt "main.dart (document_start_javascript)"?>
+```dart
+final DocumentStartJavaScriptRegistration documentStartJavaScriptRegistration = await webViewController
+    .addDocumentStartJavaScript(
+      'window.exampleValue = "Hello from a document start script!";',
+    );
+```
+
+The script runs in every frame of the document, including cross-origin `<iframe>`s, so it should not
+contain sensitive data. Calling `remove()` on the returned registration deregisters it, stopping
+JavaScript injection into future document loads. The registration can be discarded if the script
+should be injected for the lifetime of the controller.
+
+This feature is not available on the web, or on Android devices whose WebView does not support the
+`DOCUMENT_START_SCRIPT` feature; an `UnsupportedError` is thrown in those cases.
+
 ### Platform-Specific Features
 
 Many classes have a subclass or an underlying implementation that provides access to platform-specific
diff --git a/packages/webview_flutter/webview_flutter/example/lib/main.dart b/packages/webview_flutter/webview_flutter/example/lib/main.dart
index f713b14e7343..26a5930f18b6 100644
--- a/packages/webview_flutter/webview_flutter/example/lib/main.dart
+++ b/packages/webview_flutter/webview_flutter/example/lib/main.dart
@@ -111,6 +111,27 @@ const String kLogExamplePage = '''
 </html>
 ''';
 
+const String kDocumentStartExamplePage = '''
+<!DOCTYPE html>
+<html lang="en">
+<head>
+<title>Document start script example</title>
+</head>
+<body>
+
+<h1>Document start script demo page</h1>
+<p id="message">The document start script did not run.</p>
+
+<script>
+  document.getElementById('message').textContent =
+      'The document start script set window.exampleValue to: ' +
+      window.exampleValue;
+</script>
+
+</body>
+</html>
+''';
+
 class WebViewExample extends StatefulWidget {
   const WebViewExample({super.key});
 
@@ -303,6 +324,7 @@ enum MenuOptions {
   setCookie,
   logExample,
   basicAuthentication,
+  documentStartJavaScript,
 }
 
 class SampleMenu extends StatelessWidget {
@@ -311,6 +333,8 @@ class SampleMenu extends StatelessWidget {
   final WebViewController webViewController;
   late final WebViewCookieManager cookieManager = WebViewCookieManager();
 
+  static DocumentStartJavaScriptRegistration? _documentStartJavaScriptRegistration;
+
   @override
   Widget build(BuildContext context) {
     return PopupMenuButton<MenuOptions>(
@@ -347,6 +371,8 @@ class SampleMenu extends StatelessWidget {
             _onLogExample();
           case MenuOptions.basicAuthentication:
             _promptForUrl(context);
+          case MenuOptions.documentStartJavaScript:
+            _onDocumentStartJavaScriptExample(context);
         }
       },
       itemBuilder: (BuildContext context) => <PopupMenuItem<MenuOptions>>[
@@ -399,6 +425,10 @@ class SampleMenu extends StatelessWidget {
           value: MenuOptions.basicAuthentication,
           child: Text('Basic Authentication Example'),
         ),
+        const PopupMenuItem<MenuOptions>(
+          value: MenuOptions.documentStartJavaScript,
+          child: Text('Document start JavaScript example'),
+        ),
       ],
     );
   }
@@ -511,6 +541,35 @@ class SampleMenu extends StatelessWidget {
     return webViewController.loadHtmlString(kTransparentBackgroundPage);
   }
 
+  Future<void> _onDocumentStartJavaScriptExample(BuildContext context) async {
+    // Removing the previously added registration keeps this example from
+    // injecting the same JavaScript again every time it is run.
+    await _documentStartJavaScriptRegistration?.remove();
+    _documentStartJavaScriptRegistration = null;
+
+    try {
+      // #docregion document_start_javascript
+      final DocumentStartJavaScriptRegistration documentStartJavaScriptRegistration =
+          await webViewController.addDocumentStartJavaScript(
+            'window.exampleValue = "Hello from a document start script!";',
+          );
+      // #enddocregion document_start_javascript
+      _documentStartJavaScriptRegistration = documentStartJavaScriptRegistration;
+    } on UnsupportedError {
+      if (context.mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(
+            content: Text('Document start JavaScript is not supported on this platform.'),
+          ),
+        );
+      }
+      return;
+    }
+
+    // The script only affects documents that are loaded after it is added.
+    await webViewController.loadHtmlString(kDocumentStartExamplePage);
+  }
+
   Widget _getCookieList(List<WebViewCookie> cookies) {
     if (cookies.isEmpty) {
       return Container();
diff --git a/packages/webview_flutter/webview_flutter/lib/src/webview_controller.dart b/packages/webview_flutter/webview_flutter/lib/src/webview_controller.dart
index 8eb49913bf97..d20ccd224907 100644
--- a/packages/webview_flutter/webview_flutter/lib/src/webview_controller.dart
+++ b/packages/webview_flutter/webview_flutter/lib/src/webview_controller.dart
@@ -236,6 +236,30 @@ class WebViewController {
     return platform.runJavaScript(javaScript);
   }
 
+  /// Adds JavaScript that runs at the start of future document loads.
+  ///
+  /// This method should be called before loading a page if the script needs to
+  /// run for that page. It does not run JavaScript in the currently loaded
+  /// document. Scripts run in the order in which they were added.
+  ///
+  /// The script runs in every frame of a loaded document, regardless of its
+  /// origin, including cross-origin `<iframe>`s, so it should not contain
+  /// sensitive data.
+  ///
+  /// The returned [DocumentStartJavaScriptRegistration] can be used to stop injecting the
+  /// JavaScript into future document loads. It can be discarded if the
+  /// JavaScript should be injected for the lifetime of this controller.
+  ///
+  /// Throws an [UnsupportedError] if the current platform does not support
+  /// document-start JavaScript injection. This is currently the case on the
+  /// web, and on Android when the WebView installed on the device does not
+  /// support the `DOCUMENT_START_SCRIPT` feature.
+  Future<DocumentStartJavaScriptRegistration> addDocumentStartJavaScript(String javaScript) async {
+    return DocumentStartJavaScriptRegistration.fromPlatform(
+      await platform.addDocumentStartJavaScript(javaScript),
+    );
+  }
+
   /// Runs the given JavaScript in the context of the current page, and returns
   /// the result.
   ///
@@ -423,6 +447,22 @@ class WebViewController {
   }
 }
 
+/// A registration for JavaScript injected at the start of future document loads.
+///
+/// Returned by [WebViewController.addDocumentStartJavaScript].
+class DocumentStartJavaScriptRegistration {
+  /// Constructs a [DocumentStartJavaScriptRegistration] from a specific platform
+  /// implementation.
+  DocumentStartJavaScriptRegistration.fromPlatform(this.platform);
+
+  /// Implementation of [PlatformDocumentStartJavaScriptRegistration] for the current
+  /// platform.
+  final PlatformDocumentStartJavaScriptRegistration platform;
+
+  /// Deregisters this registration, stopping JavaScript injection into future document loads.
+  Future<void> remove() => platform.remove();
+}
+
 /// Permissions request when web content requests access to protected resources.
 ///
 /// A response MUST be provided by calling [grant], [deny], or a method from
diff --git a/packages/webview_flutter/webview_flutter/lib/webview_flutter.dart b/packages/webview_flutter/webview_flutter/lib/webview_flutter.dart
index 9e1d8082ffb2..616136010db4 100644
--- a/packages/webview_flutter/webview_flutter/lib/webview_flutter.dart
+++ b/packages/webview_flutter/webview_flutter/lib/webview_flutter.dart
@@ -19,6 +19,7 @@ export 'package:webview_flutter_platform_interface/webview_flutter_platform_inte
         NavigationRequest,
         NavigationRequestCallback,
         PageEventCallback,
+        PlatformDocumentStartJavaScriptRegistration,
         PlatformNavigationDelegateCreationParams,
         PlatformWebViewControllerCreationParams,
         PlatformWebViewCookieManagerCreationParams,
diff --git a/packages/webview_flutter/webview_flutter/pubspec.yaml b/packages/webview_flutter/webview_flutter/pubspec.yaml
index a8bfde8791cd..3df201f35f74 100644
--- a/packages/webview_flutter/webview_flutter/pubspec.yaml
+++ b/packages/webview_flutter/webview_flutter/pubspec.yaml
@@ -2,7 +2,7 @@ name: webview_flutter
 description: A Flutter plugin that provides a WebView widget backed by the system webview.
 repository: https://github.com/flutter/packages/tree/main/packages/webview_flutter/webview_flutter
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+webview%22
-version: 4.14.1
+version: 4.15.0
 
 environment:
   sdk: ^3.10.0
@@ -21,9 +21,9 @@ flutter:
 dependencies:
   flutter:
     sdk: flutter
-  webview_flutter_android: ^4.12.0
-  webview_flutter_platform_interface: ^2.15.1
-  webview_flutter_wkwebview: ^3.25.1
+  webview_flutter_android: ^4.15.0
+  webview_flutter_platform_interface: ^2.16.0
+  webview_flutter_wkwebview: ^3.27.0
 
 dev_dependencies:
   build_runner: ^2.1.5
diff --git a/packages/webview_flutter/webview_flutter/test/webview_controller_test.dart b/packages/webview_flutter/webview_flutter/test/webview_controller_test.dart
index 20948e950ff7..38c5e53b1e85 100644
--- a/packages/webview_flutter/webview_flutter/test/webview_controller_test.dart
+++ b/packages/webview_flutter/webview_flutter/test/webview_controller_test.dart
@@ -13,7 +13,11 @@ import 'package:webview_flutter_platform_interface/webview_flutter_platform_inte
 
 import 'webview_controller_test.mocks.dart';
 
-@GenerateMocks(<Type>[PlatformWebViewController, PlatformNavigationDelegate])
+@GenerateMocks(<Type>[
+  PlatformWebViewController,
+  PlatformNavigationDelegate,
+  PlatformDocumentStartJavaScriptRegistration,
+])
 void main() {
   test('loadFile', () async {
     final mockPlatformWebViewController = MockPlatformWebViewController();
@@ -146,6 +150,40 @@ void main() {
     verify(mockPlatformWebViewController.runJavaScript('1 + 1'));
   });
 
+  test('addDocumentStartJavaScript', () async {
+    final mockPlatformWebViewController = MockPlatformWebViewController();
+    final mockPlatformDocumentStartJavaScriptRegistration =
+        MockPlatformDocumentStartJavaScriptRegistration();
+    when(
+      mockPlatformWebViewController.addDocumentStartJavaScript('window.test = true;'),
+    ).thenAnswer((_) async => mockPlatformDocumentStartJavaScriptRegistration);
+
+    final webViewController = WebViewController.fromPlatform(mockPlatformWebViewController);
+
+    final DocumentStartJavaScriptRegistration documentStartJavaScript = await webViewController
+        .addDocumentStartJavaScript('window.test = true;');
+
+    verify(mockPlatformWebViewController.addDocumentStartJavaScript('window.test = true;'));
+    expect(documentStartJavaScript.platform, mockPlatformDocumentStartJavaScriptRegistration);
+  });
+
+  test('DocumentStartJavaScriptRegistration.remove', () async {
+    final mockPlatformWebViewController = MockPlatformWebViewController();
+    final mockPlatformDocumentStartJavaScriptRegistration =
+        MockPlatformDocumentStartJavaScriptRegistration();
+    when(
+      mockPlatformWebViewController.addDocumentStartJavaScript('window.test = true;'),
+    ).thenAnswer((_) async => mockPlatformDocumentStartJavaScriptRegistration);
+
+    final webViewController = WebViewController.fromPlatform(mockPlatformWebViewController);
+
+    final DocumentStartJavaScriptRegistration documentStartJavaScript = await webViewController
+        .addDocumentStartJavaScript('window.test = true;');
+    await documentStartJavaScript.remove();
+
+    verify(mockPlatformDocumentStartJavaScriptRegistration.remove());
+  });
+
   test('runJavaScriptReturningResult', () async {
     final mockPlatformWebViewController = MockPlatformWebViewController();
     when(
diff --git a/packages/webview_flutter/webview_flutter/test/webview_controller_test.mocks.dart b/packages/webview_flutter/webview_flutter/test/webview_controller_test.mocks.dart
index 8f419af62120..00817c688301 100644
--- a/packages/webview_flutter/webview_flutter/test/webview_controller_test.mocks.dart
+++ b/packages/webview_flutter/webview_flutter/test/webview_controller_test.mocks.dart
@@ -4,11 +4,11 @@
 
 // ignore_for_file: no_leading_underscores_for_library_prefixes
 import 'dart:async' as _i5;
-import 'dart:ui' as _i3;
+import 'dart:ui' as _i4;
 
 import 'package:mockito/mockito.dart' as _i1;
 import 'package:webview_flutter_platform_interface/src/platform_navigation_delegate.dart' as _i6;
-import 'package:webview_flutter_platform_interface/src/platform_webview_controller.dart' as _i4;
+import 'package:webview_flutter_platform_interface/src/platform_webview_controller.dart' as _i3;
 import 'package:webview_flutter_platform_interface/src/types/types.dart' as _i2;
 
 // ignore_for_file: type=lint
@@ -32,24 +32,30 @@ class _FakePlatformWebViewControllerCreationParams_0 extends _i1.SmartFake
     : super(parent, parentInvocation);
 }
 
-class _FakeObject_1 extends _i1.SmartFake implements Object {
-  _FakeObject_1(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakePlatformDocumentStartJavaScriptRegistration_1 extends _i1.SmartFake
+    implements _i3.PlatformDocumentStartJavaScriptRegistration {
+  _FakePlatformDocumentStartJavaScriptRegistration_1(Object parent, Invocation parentInvocation)
+    : super(parent, parentInvocation);
+}
+
+class _FakeObject_2 extends _i1.SmartFake implements Object {
+  _FakeObject_2(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
-class _FakeOffset_2 extends _i1.SmartFake implements _i3.Offset {
-  _FakeOffset_2(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakeOffset_3 extends _i1.SmartFake implements _i4.Offset {
+  _FakeOffset_3(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
-class _FakePlatformNavigationDelegateCreationParams_3 extends _i1.SmartFake
+class _FakePlatformNavigationDelegateCreationParams_4 extends _i1.SmartFake
     implements _i2.PlatformNavigationDelegateCreationParams {
-  _FakePlatformNavigationDelegateCreationParams_3(Object parent, Invocation parentInvocation)
+  _FakePlatformNavigationDelegateCreationParams_4(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
 /// A class which mocks [PlatformWebViewController].
 ///
 /// See the documentation for Mockito's code generation for more information.
-class MockPlatformWebViewController extends _i1.Mock implements _i4.PlatformWebViewController {
+class MockPlatformWebViewController extends _i1.Mock implements _i3.PlatformWebViewController {
   MockPlatformWebViewController() {
     _i1.throwOnMissingStub(this);
   }
@@ -197,18 +203,33 @@ class MockPlatformWebViewController extends _i1.Mock implements _i4.PlatformWebV
           )
           as _i5.Future<void>);
 
+  @override
+  _i5.Future<_i3.PlatformDocumentStartJavaScriptRegistration> addDocumentStartJavaScript(
+    String? javaScript,
+  ) =>
+      (super.noSuchMethod(
+            Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+            returnValue: _i5.Future<_i3.PlatformDocumentStartJavaScriptRegistration>.value(
+              _FakePlatformDocumentStartJavaScriptRegistration_1(
+                this,
+                Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+              ),
+            ),
+          )
+          as _i5.Future<_i3.PlatformDocumentStartJavaScriptRegistration>);
+
   @override
   _i5.Future<Object> runJavaScriptReturningResult(String? javaScript) =>
       (super.noSuchMethod(
             Invocation.method(#runJavaScriptReturningResult, [javaScript]),
             returnValue: _i5.Future<Object>.value(
-              _FakeObject_1(this, Invocation.method(#runJavaScriptReturningResult, [javaScript])),
+              _FakeObject_2(this, Invocation.method(#runJavaScriptReturningResult, [javaScript])),
             ),
           )
           as _i5.Future<Object>);
 
   @override
-  _i5.Future<void> addJavaScriptChannel(_i4.JavaScriptChannelParams? javaScriptChannelParams) =>
+  _i5.Future<void> addJavaScriptChannel(_i3.JavaScriptChannelParams? javaScriptChannelParams) =>
       (super.noSuchMethod(
             Invocation.method(#addJavaScriptChannel, [javaScriptChannelParams]),
             returnValue: _i5.Future<void>.value(),
@@ -275,14 +296,14 @@ class MockPlatformWebViewController extends _i1.Mock implements _i4.PlatformWebV
           as bool);
 
   @override
-  _i5.Future<_i3.Offset> getScrollPosition() =>
+  _i5.Future<_i4.Offset> getScrollPosition() =>
       (super.noSuchMethod(
             Invocation.method(#getScrollPosition, []),
-            returnValue: _i5.Future<_i3.Offset>.value(
-              _FakeOffset_2(this, Invocation.method(#getScrollPosition, [])),
+            returnValue: _i5.Future<_i4.Offset>.value(
+              _FakeOffset_3(this, Invocation.method(#getScrollPosition, [])),
             ),
           )
-          as _i5.Future<_i3.Offset>);
+          as _i5.Future<_i4.Offset>);
 
   @override
   _i5.Future<void> enableZoom(bool? enabled) =>
@@ -294,7 +315,7 @@ class MockPlatformWebViewController extends _i1.Mock implements _i4.PlatformWebV
           as _i5.Future<void>);
 
   @override
-  _i5.Future<void> setBackgroundColor(_i3.Color? color) =>
+  _i5.Future<void> setBackgroundColor(_i4.Color? color) =>
       (super.noSuchMethod(
             Invocation.method(#setBackgroundColor, [color]),
             returnValue: _i5.Future<void>.value(),
@@ -416,7 +437,7 @@ class MockPlatformNavigationDelegate extends _i1.Mock implements _i6.PlatformNav
   _i2.PlatformNavigationDelegateCreationParams get params =>
       (super.noSuchMethod(
             Invocation.getter(#params),
-            returnValue: _FakePlatformNavigationDelegateCreationParams_3(
+            returnValue: _FakePlatformNavigationDelegateCreationParams_4(
               this,
               Invocation.getter(#params),
             ),
@@ -504,3 +525,22 @@ class MockPlatformNavigationDelegate extends _i1.Mock implements _i6.PlatformNav
           )
           as _i5.Future<void>);
 }
+
+/// A class which mocks [PlatformDocumentStartJavaScriptRegistration].
+///
+/// See the documentation for Mockito's code generation for more information.
+class MockPlatformDocumentStartJavaScriptRegistration extends _i1.Mock
+    implements _i3.PlatformDocumentStartJavaScriptRegistration {
+  MockPlatformDocumentStartJavaScriptRegistration() {
+    _i1.throwOnMissingStub(this);
+  }
+
+  @override
+  _i5.Future<void> remove() =>
+      (super.noSuchMethod(
+            Invocation.method(#remove, []),
+            returnValue: _i5.Future<void>.value(),
+            returnValueForMissingStub: _i5.Future<void>.value(),
+          )
+          as _i5.Future<void>);
+}
diff --git a/packages/webview_flutter/webview_flutter/test/webview_widget_test.mocks.dart b/packages/webview_flutter/webview_flutter/test/webview_widget_test.mocks.dart
index 8126ad33a79c..5c3130cb707f 100644
--- a/packages/webview_flutter/webview_flutter/test/webview_widget_test.mocks.dart
+++ b/packages/webview_flutter/webview_flutter/test/webview_widget_test.mocks.dart
@@ -4,13 +4,13 @@
 
 // ignore_for_file: no_leading_underscores_for_library_prefixes
 import 'dart:async' as _i7;
-import 'dart:ui' as _i3;
+import 'dart:ui' as _i4;
 
-import 'package:flutter/foundation.dart' as _i5;
-import 'package:flutter/widgets.dart' as _i4;
+import 'package:flutter/foundation.dart' as _i6;
+import 'package:flutter/widgets.dart' as _i5;
 import 'package:mockito/mockito.dart' as _i1;
 import 'package:webview_flutter_platform_interface/src/platform_navigation_delegate.dart' as _i8;
-import 'package:webview_flutter_platform_interface/src/platform_webview_controller.dart' as _i6;
+import 'package:webview_flutter_platform_interface/src/platform_webview_controller.dart' as _i3;
 import 'package:webview_flutter_platform_interface/src/platform_webview_widget.dart' as _i9;
 import 'package:webview_flutter_platform_interface/src/types/types.dart' as _i2;
 
@@ -35,31 +35,37 @@ class _FakePlatformWebViewControllerCreationParams_0 extends _i1.SmartFake
     : super(parent, parentInvocation);
 }
 
-class _FakeObject_1 extends _i1.SmartFake implements Object {
-  _FakeObject_1(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakePlatformDocumentStartJavaScriptRegistration_1 extends _i1.SmartFake
+    implements _i3.PlatformDocumentStartJavaScriptRegistration {
+  _FakePlatformDocumentStartJavaScriptRegistration_1(Object parent, Invocation parentInvocation)
+    : super(parent, parentInvocation);
+}
+
+class _FakeObject_2 extends _i1.SmartFake implements Object {
+  _FakeObject_2(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
-class _FakeOffset_2 extends _i1.SmartFake implements _i3.Offset {
-  _FakeOffset_2(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakeOffset_3 extends _i1.SmartFake implements _i4.Offset {
+  _FakeOffset_3(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
-class _FakePlatformWebViewWidgetCreationParams_3 extends _i1.SmartFake
+class _FakePlatformWebViewWidgetCreationParams_4 extends _i1.SmartFake
     implements _i2.PlatformWebViewWidgetCreationParams {
-  _FakePlatformWebViewWidgetCreationParams_3(Object parent, Invocation parentInvocation)
+  _FakePlatformWebViewWidgetCreationParams_4(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeWidget_4 extends _i1.SmartFake implements _i4.Widget {
-  _FakeWidget_4(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakeWidget_5 extends _i1.SmartFake implements _i5.Widget {
+  _FakeWidget_5(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 
   @override
-  String toString({_i5.DiagnosticLevel? minLevel = _i5.DiagnosticLevel.info}) => super.toString();
+  String toString({_i6.DiagnosticLevel? minLevel = _i6.DiagnosticLevel.info}) => super.toString();
 }
 
 /// A class which mocks [PlatformWebViewController].
 ///
 /// See the documentation for Mockito's code generation for more information.
-class MockPlatformWebViewController extends _i1.Mock implements _i6.PlatformWebViewController {
+class MockPlatformWebViewController extends _i1.Mock implements _i3.PlatformWebViewController {
   MockPlatformWebViewController() {
     _i1.throwOnMissingStub(this);
   }
@@ -207,18 +213,33 @@ class MockPlatformWebViewController extends _i1.Mock implements _i6.PlatformWebV
           )
           as _i7.Future<void>);
 
+  @override
+  _i7.Future<_i3.PlatformDocumentStartJavaScriptRegistration> addDocumentStartJavaScript(
+    String? javaScript,
+  ) =>
+      (super.noSuchMethod(
+            Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+            returnValue: _i7.Future<_i3.PlatformDocumentStartJavaScriptRegistration>.value(
+              _FakePlatformDocumentStartJavaScriptRegistration_1(
+                this,
+                Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+              ),
+            ),
+          )
+          as _i7.Future<_i3.PlatformDocumentStartJavaScriptRegistration>);
+
   @override
   _i7.Future<Object> runJavaScriptReturningResult(String? javaScript) =>
       (super.noSuchMethod(
             Invocation.method(#runJavaScriptReturningResult, [javaScript]),
             returnValue: _i7.Future<Object>.value(
-              _FakeObject_1(this, Invocation.method(#runJavaScriptReturningResult, [javaScript])),
+              _FakeObject_2(this, Invocation.method(#runJavaScriptReturningResult, [javaScript])),
             ),
           )
           as _i7.Future<Object>);
 
   @override
-  _i7.Future<void> addJavaScriptChannel(_i6.JavaScriptChannelParams? javaScriptChannelParams) =>
+  _i7.Future<void> addJavaScriptChannel(_i3.JavaScriptChannelParams? javaScriptChannelParams) =>
       (super.noSuchMethod(
             Invocation.method(#addJavaScriptChannel, [javaScriptChannelParams]),
             returnValue: _i7.Future<void>.value(),
@@ -285,14 +306,14 @@ class MockPlatformWebViewController extends _i1.Mock implements _i6.PlatformWebV
           as bool);
 
   @override
-  _i7.Future<_i3.Offset> getScrollPosition() =>
+  _i7.Future<_i4.Offset> getScrollPosition() =>
       (super.noSuchMethod(
             Invocation.method(#getScrollPosition, []),
-            returnValue: _i7.Future<_i3.Offset>.value(
-              _FakeOffset_2(this, Invocation.method(#getScrollPosition, [])),
+            returnValue: _i7.Future<_i4.Offset>.value(
+              _FakeOffset_3(this, Invocation.method(#getScrollPosition, [])),
             ),
           )
-          as _i7.Future<_i3.Offset>);
+          as _i7.Future<_i4.Offset>);
 
   @override
   _i7.Future<void> enableZoom(bool? enabled) =>
@@ -304,7 +325,7 @@ class MockPlatformWebViewController extends _i1.Mock implements _i6.PlatformWebV
           as _i7.Future<void>);
 
   @override
-  _i7.Future<void> setBackgroundColor(_i3.Color? color) =>
+  _i7.Future<void> setBackgroundColor(_i4.Color? color) =>
       (super.noSuchMethod(
             Invocation.method(#setBackgroundColor, [color]),
             returnValue: _i7.Future<void>.value(),
@@ -426,7 +447,7 @@ class MockPlatformWebViewWidget extends _i1.Mock implements _i9.PlatformWebViewW
   _i2.PlatformWebViewWidgetCreationParams get params =>
       (super.noSuchMethod(
             Invocation.getter(#params),
-            returnValue: _FakePlatformWebViewWidgetCreationParams_3(
+            returnValue: _FakePlatformWebViewWidgetCreationParams_4(
               this,
               Invocation.getter(#params),
             ),
@@ -434,10 +455,10 @@ class MockPlatformWebViewWidget extends _i1.Mock implements _i9.PlatformWebViewW
           as _i2.PlatformWebViewWidgetCreationParams);
 
   @override
-  _i4.Widget build(_i4.BuildContext? context) =>
+  _i5.Widget build(_i5.BuildContext? context) =>
       (super.noSuchMethod(
             Invocation.method(#build, [context]),
-            returnValue: _FakeWidget_4(this, Invocation.method(#build, [context])),
+            returnValue: _FakeWidget_5(this, Invocation.method(#build, [context])),
           )
-          as _i4.Widget);
+          as _i5.Widget);
 }
diff --git a/packages/webview_flutter/webview_flutter_android/CHANGELOG.md b/packages/webview_flutter/webview_flutter_android/CHANGELOG.md
index b464989abeea..34e8b8798422 100644
--- a/packages/webview_flutter/webview_flutter_android/CHANGELOG.md
+++ b/packages/webview_flutter/webview_flutter_android/CHANGELOG.md
@@ -1,4 +1,9 @@
+## 4.15.0
+
+* Adds support for `addDocumentStartJavaScript`.
+
 ## 4.14.0
+
 * Adds support for configuring Web Authentication in `AndroidWebViewController` with `setWebAuthenticationSupport` to enable Passkey and other related Authentication.
 
 ## 4.13.0
diff --git a/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/AndroidWebkitLibrary.g.kt b/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/AndroidWebkitLibrary.g.kt
index 651b288a49db..51e274854f6d 100644
--- a/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/AndroidWebkitLibrary.g.kt
+++ b/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/AndroidWebkitLibrary.g.kt
@@ -609,6 +609,12 @@ abstract class AndroidWebkitLibraryPigeonProxyApiRegistrar(val binaryMessenger:
    */
   abstract fun getPigeonApiWebViewFeature(): PigeonApiWebViewFeature
 
+  /**
+   * An implementation of [PigeonApiScriptHandler] used to add a new Dart instance of
+   * `ScriptHandler` to the Dart `InstanceManager`.
+   */
+  abstract fun getPigeonApiScriptHandler(): PigeonApiScriptHandler
+
   fun setUp() {
     AndroidWebkitLibraryPigeonInstanceManagerApi.setUpMessageHandlers(
         binaryMessenger, instanceManager)
@@ -643,6 +649,7 @@ abstract class AndroidWebkitLibraryPigeonProxyApiRegistrar(val binaryMessenger:
     PigeonApiWebSettingsCompat.setUpMessageHandlers(
         binaryMessenger, getPigeonApiWebSettingsCompat())
     PigeonApiWebViewFeature.setUpMessageHandlers(binaryMessenger, getPigeonApiWebViewFeature())
+    PigeonApiScriptHandler.setUpMessageHandlers(binaryMessenger, getPigeonApiScriptHandler())
   }
 
   fun tearDown() {
@@ -670,6 +677,7 @@ abstract class AndroidWebkitLibraryPigeonProxyApiRegistrar(val binaryMessenger:
     PigeonApiCertificate.setUpMessageHandlers(binaryMessenger, null)
     PigeonApiWebSettingsCompat.setUpMessageHandlers(binaryMessenger, null)
     PigeonApiWebViewFeature.setUpMessageHandlers(binaryMessenger, null)
+    PigeonApiScriptHandler.setUpMessageHandlers(binaryMessenger, null)
   }
 }
 
@@ -913,6 +921,12 @@ private class AndroidWebkitLibraryPigeonProxyApiBaseCodec(
           logNewInstanceFailure("WebViewFeature", value, it.exceptionOrNull())
         }
       }
+    } else if (value is androidx.webkit.ScriptHandler) {
+      registrar.getPigeonApiScriptHandler().pigeon_newInstance(value) {
+        if (it.isFailure) {
+          logNewInstanceFailure("ScriptHandler", value, it.exceptionOrNull())
+        }
+      }
     }
 
     when {
@@ -1815,6 +1829,12 @@ abstract class PigeonApiWebView(
       callback: (Result<String?>) -> Unit
   )
 
+  /** Adds JavaScript that runs at the start of future document loads. */
+  abstract fun addDocumentStartJavaScript(
+      pigeon_instance: android.webkit.WebView,
+      javaScript: String
+  ): androidx.webkit.ScriptHandler
+
   /** Gets the title for the current page. */
   abstract fun getTitle(pigeon_instance: android.webkit.WebView): String?
 
@@ -2202,6 +2222,29 @@ abstract class PigeonApiWebView(
           channel.setMessageHandler(null)
         }
       }
+      run {
+        val channel =
+            BasicMessageChannel<Any?>(
+                binaryMessenger,
+                "dev.flutter.pigeon.webview_flutter_android.WebView.addDocumentStartJavaScript",
+                codec)
+        if (api != null) {
+          channel.setMessageHandler { message, reply ->
+            val args = message as List<Any?>
+            val pigeon_instanceArg = args[0] as android.webkit.WebView
+            val javaScriptArg = args[1] as String
+            val wrapped: List<Any?> =
+                try {
+                  listOf(api.addDocumentStartJavaScript(pigeon_instanceArg, javaScriptArg))
+                } catch (exception: Throwable) {
+                  AndroidWebkitLibraryPigeonUtils.wrapError(exception)
+                }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
       run {
         val channel =
             BasicMessageChannel<Any?>(
@@ -6997,3 +7040,82 @@ abstract class PigeonApiWebViewFeature(
     }
   }
 }
+/**
+ * Handle to a document start JavaScript that was added with `WebView.addDocumentStartJavaScript`.
+ *
+ * See https://developer.android.com/reference/kotlin/androidx/webkit/ScriptHandler.
+ */
+@Suppress("UNCHECKED_CAST")
+abstract class PigeonApiScriptHandler(
+    open val pigeonRegistrar: AndroidWebkitLibraryPigeonProxyApiRegistrar
+) {
+  /** Removes the script from the WebView. */
+  abstract fun remove(pigeon_instance: androidx.webkit.ScriptHandler)
+
+  companion object {
+    @Suppress("LocalVariableName")
+    fun setUpMessageHandlers(binaryMessenger: BinaryMessenger, api: PigeonApiScriptHandler?) {
+      val codec = api?.pigeonRegistrar?.codec ?: AndroidWebkitLibraryPigeonCodec()
+      run {
+        val channel =
+            BasicMessageChannel<Any?>(
+                binaryMessenger,
+                "dev.flutter.pigeon.webview_flutter_android.ScriptHandler.remove",
+                codec)
+        if (api != null) {
+          channel.setMessageHandler { message, reply ->
+            val args = message as List<Any?>
+            val pigeon_instanceArg = args[0] as androidx.webkit.ScriptHandler
+            val wrapped: List<Any?> =
+                try {
+                  api.remove(pigeon_instanceArg)
+                  listOf(null)
+                } catch (exception: Throwable) {
+                  AndroidWebkitLibraryPigeonUtils.wrapError(exception)
+                }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
+    }
+  }
+
+  @Suppress("LocalVariableName", "FunctionName")
+  /** Creates a Dart instance of ScriptHandler and attaches it to [pigeon_instanceArg]. */
+  fun pigeon_newInstance(
+      pigeon_instanceArg: androidx.webkit.ScriptHandler,
+      callback: (Result<Unit>) -> Unit
+  ) {
+    if (pigeonRegistrar.ignoreCallsToDart) {
+      callback(
+          Result.failure(
+              AndroidWebKitError("ignore-calls-error", "Calls to Dart are being ignored.", "")))
+    } else if (pigeonRegistrar.instanceManager.containsInstance(pigeon_instanceArg)) {
+      callback(Result.success(Unit))
+    } else {
+      val pigeon_identifierArg =
+          pigeonRegistrar.instanceManager.addHostCreatedInstance(pigeon_instanceArg)
+      val binaryMessenger = pigeonRegistrar.binaryMessenger
+      val codec = pigeonRegistrar.codec
+      val channelName =
+          "dev.flutter.pigeon.webview_flutter_android.ScriptHandler.pigeon_newInstance"
+      val channel = BasicMessageChannel<Any?>(binaryMessenger, channelName, codec)
+      channel.send(listOf(pigeon_identifierArg)) {
+        if (it is List<*>) {
+          if (it.size > 1) {
+            callback(
+                Result.failure(
+                    AndroidWebKitError(it[0] as String, it[1] as String, it[2] as String?)))
+          } else {
+            callback(Result.success(Unit))
+          }
+        } else {
+          callback(
+              Result.failure(AndroidWebkitLibraryPigeonUtils.createConnectionError(channelName)))
+        }
+      }
+    }
+  }
+}
diff --git a/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/ProxyApiRegistrar.java b/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/ProxyApiRegistrar.java
index 73848e0968c1..173ccd686de3 100644
--- a/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/ProxyApiRegistrar.java
+++ b/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/ProxyApiRegistrar.java
@@ -261,4 +261,10 @@ public PigeonApiWebViewFeature getPigeonApiWebViewFeature() {
   public PigeonApiWebSettingsCompat getPigeonApiWebSettingsCompat() {
     return new WebSettingsCompatProxyApi(this);
   }
+
+  @NonNull
+  @Override
+  public PigeonApiScriptHandler getPigeonApiScriptHandler() {
+    return new ScriptHandlerProxyApi(this);
+  }
 }
diff --git a/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/ScriptHandlerProxyApi.java b/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/ScriptHandlerProxyApi.java
new file mode 100644
index 000000000000..86e306915b15
--- /dev/null
+++ b/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/ScriptHandlerProxyApi.java
@@ -0,0 +1,25 @@
+// Copyright 2013 The Flutter Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package io.flutter.plugins.webviewflutter;
+
+import androidx.annotation.NonNull;
+import androidx.webkit.ScriptHandler;
+
+/**
+ * Proxy API implementation for {@link ScriptHandler}.
+ *
+ * <p>This class may handle instantiating and adding native object instances that are attached to a
+ * Dart instance or handle method calls on the associated native class or an instance of the class.
+ */
+public class ScriptHandlerProxyApi extends PigeonApiScriptHandler {
+  public ScriptHandlerProxyApi(@NonNull ProxyApiRegistrar pigeonRegistrar) {
+    super(pigeonRegistrar);
+  }
+
+  @Override
+  public void remove(@NonNull ScriptHandler pigeon_instance) {
+    pigeon_instance.remove();
+  }
+}
diff --git a/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/WebViewProxyApi.java b/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/WebViewProxyApi.java
index e3016db2845d..2f9e8add5f63 100644
--- a/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/WebViewProxyApi.java
+++ b/packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/WebViewProxyApi.java
@@ -17,8 +17,11 @@
 import android.webkit.WebViewClient;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.webkit.ScriptHandler;
+import androidx.webkit.WebViewCompat;
 import io.flutter.embedding.android.FlutterView;
 import io.flutter.plugin.platform.PlatformView;
+import java.util.Collections;
 import java.util.Map;
 import kotlin.Result;
 import kotlin.Unit;
@@ -226,6 +229,19 @@ public void evaluateJavascript(
         javascriptString, result -> ResultCompat.success(result, callback));
   }
 
+  /**
+   * This method should only be called if {@link WebViewFeatureProxyApi#isFeatureSupported(String)}
+   * with DOCUMENT_START_SCRIPT returns true.
+   */
+  @SuppressLint("RequiresFeature")
+  @NonNull
+  @Override
+  public ScriptHandler addDocumentStartJavaScript(
+      @NonNull WebView pigeon_instance, @NonNull String javaScript) {
+    return WebViewCompat.addDocumentStartJavaScript(
+        pigeon_instance, javaScript, Collections.singleton("*"));
+  }
+
   @Nullable
   @Override
   public String getTitle(@NonNull WebView pigeon_instance) {
diff --git a/packages/webview_flutter/webview_flutter_android/android/src/test/java/io/flutter/plugins/webviewflutter/ScriptHandlerTest.java b/packages/webview_flutter/webview_flutter_android/android/src/test/java/io/flutter/plugins/webviewflutter/ScriptHandlerTest.java
new file mode 100644
index 000000000000..3db51b604569
--- /dev/null
+++ b/packages/webview_flutter/webview_flutter_android/android/src/test/java/io/flutter/plugins/webviewflutter/ScriptHandlerTest.java
@@ -0,0 +1,23 @@
+// Copyright 2013 The Flutter Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package io.flutter.plugins.webviewflutter;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+import androidx.webkit.ScriptHandler;
+import org.junit.Test;
+
+public class ScriptHandlerTest {
+  @Test
+  public void remove() {
+    final PigeonApiScriptHandler api = new TestProxyApiRegistrar().getPigeonApiScriptHandler();
+
+    final ScriptHandler instance = mock(ScriptHandler.class);
+    api.remove(instance);
+
+    verify(instance).remove();
+  }
+}
diff --git a/packages/webview_flutter/webview_flutter_android/android/src/test/java/io/flutter/plugins/webviewflutter/WebViewTest.java b/packages/webview_flutter/webview_flutter_android/android/src/test/java/io/flutter/plugins/webviewflutter/WebViewTest.java
index 8ad8b29df915..7a57c0cbc756 100644
--- a/packages/webview_flutter/webview_flutter_android/android/src/test/java/io/flutter/plugins/webviewflutter/WebViewTest.java
+++ b/packages/webview_flutter/webview_flutter_android/android/src/test/java/io/flutter/plugins/webviewflutter/WebViewTest.java
@@ -10,6 +10,7 @@
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
@@ -19,11 +20,15 @@
 import android.webkit.ValueCallback;
 import android.webkit.WebView;
 import android.webkit.WebViewClient;
+import androidx.webkit.ScriptHandler;
+import androidx.webkit.WebViewCompat;
 import io.flutter.embedding.android.FlutterView;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import org.junit.Test;
 import org.mockito.ArgumentCaptor;
+import org.mockito.MockedStatic;
 
 public class WebViewTest {
   @Test
@@ -218,6 +223,26 @@ public void evaluateJavaScript() {
     assertEquals(resultValue[0], result);
   }
 
+  @Test
+  public void addDocumentStartJavaScript() {
+    final PigeonApiWebView api = new TestProxyApiRegistrar().getPigeonApiWebView();
+
+    final WebView instance = mock(WebView.class);
+    final String script = "window.test = true;";
+    final ScriptHandler scriptHandler = mock(ScriptHandler.class);
+
+    try (MockedStatic<WebViewCompat> mockedWebViewCompat = mockStatic(WebViewCompat.class)) {
+      mockedWebViewCompat
+          .when(
+              () ->
+                  WebViewCompat.addDocumentStartJavaScript(
+                      instance, script, Collections.singleton("*")))
+          .thenReturn(scriptHandler);
+
+      assertEquals(scriptHandler, api.addDocumentStartJavaScript(instance, script));
+    }
+  }
+
   @Test
   public void getTitle() {
     final PigeonApiWebView api = new TestProxyApiRegistrar().getPigeonApiWebView();
diff --git a/packages/webview_flutter/webview_flutter_android/example/integration_test/webview_flutter_test.dart b/packages/webview_flutter/webview_flutter_android/example/integration_test/webview_flutter_test.dart
index d23c92e3a04c..0c59d8f9a2ca 100644
--- a/packages/webview_flutter/webview_flutter_android/example/integration_test/webview_flutter_test.dart
+++ b/packages/webview_flutter/webview_flutter_android/example/integration_test/webview_flutter_test.dart
@@ -36,6 +36,15 @@ Future<void> main() async {
         request.response.writeln('How are you today?');
       } else if (request.uri.path == '/headers') {
         request.response.writeln('${request.headers}');
+      } else if (request.uri.path == '/document-start.html') {
+        request.response.headers.contentType = ContentType.html;
+        // The inline script records the state of the window at parse time, so
+        // that a test can verify that injected scripts ran before it.
+        request.response.writeln(
+          '<!DOCTYPE html><html><head> '
+          '<script>window.recordedAtParseTime = String(window.injectedAtDocumentStart);</script> '
+          '</head><body>Document start test.</body></html>',
+        );
       } else if (request.uri.path == '/favicon.ico') {
         request.response.statusCode = HttpStatus.notFound;
       } else if (request.uri.path == '/http-basic-authentication') {
@@ -57,6 +66,7 @@ Future<void> main() async {
   final secondaryUrl = '$prefixUrl/secondary.txt';
   final headersUrl = '$prefixUrl/headers';
   final basicAuthUrl = '$prefixUrl/http-basic-authentication';
+  final documentStartUrl = '$prefixUrl/document-start.html';
 
   setUp(() {
     android_webkit.PigeonOverrides.pigeon_reset();
@@ -194,6 +204,44 @@ Future<void> main() async {
     await expectLater(controller.runJavaScriptReturningResult('1 + 1'), completion(2));
   });
 
+  testWidgets('addDocumentStartJavaScript', (WidgetTester tester) async {
+    final pageFinished = Completer<void>();
+    final messageReceived = Completer<String>();
+
+    final controller = PlatformWebViewController(const PlatformWebViewControllerCreationParams());
+    await controller.setJavaScriptMode(JavaScriptMode.unrestricted);
+    final delegate = PlatformNavigationDelegate(const PlatformNavigationDelegateCreationParams());
+    await delegate.setOnPageFinished((_) => pageFinished.complete());
+    await controller.setPlatformNavigationDelegate(delegate);
+    await controller.addJavaScriptChannel(
+      JavaScriptChannelParams(
+        name: 'Echo',
+        onMessageReceived: (JavaScriptMessage message) => messageReceived.complete(message.message),
+      ),
+    );
+
+    await controller.addDocumentStartJavaScript('window.injectedAtDocumentStart = "injected";');
+    await controller.loadRequest(LoadRequestParams(uri: Uri.parse(documentStartUrl)));
+
+    await tester.pumpWidget(
+      Builder(
+        builder: (BuildContext context) {
+          return PlatformWebViewWidget(
+            PlatformWebViewWidgetCreationParams(controller: controller),
+          ).build(context);
+        },
+      ),
+    );
+
+    await pageFinished.future;
+
+    // The page records this value while it is being parsed, so a match proves
+    // that the script ran before the document's own scripts.
+    await controller.runJavaScript('Echo.postMessage(window.recordedAtParseTime);');
+
+    await expectLater(messageReceived.future, completion('injected'));
+  });
+
   testWidgets('loadRequest with headers', (WidgetTester tester) async {
     final headers = <String, String>{'test_header': 'flutter_test_header'};
 
diff --git a/packages/webview_flutter/webview_flutter_android/lib/src/android_webkit.g.dart b/packages/webview_flutter/webview_flutter_android/lib/src/android_webkit.g.dart
index ec5388fd6a23..de34de406511 100644
--- a/packages/webview_flutter/webview_flutter_android/lib/src/android_webkit.g.dart
+++ b/packages/webview_flutter/webview_flutter_android/lib/src/android_webkit.g.dart
@@ -380,6 +380,7 @@ class PigeonInstanceManager {
     Certificate.pigeon_setUpMessageHandlers(pigeon_instanceManager: instanceManager);
     WebSettingsCompat.pigeon_setUpMessageHandlers(pigeon_instanceManager: instanceManager);
     WebViewFeature.pigeon_setUpMessageHandlers(pigeon_instanceManager: instanceManager);
+    ScriptHandler.pigeon_setUpMessageHandlers(pigeon_instanceManager: instanceManager);
     return instanceManager;
   }
 
@@ -1997,6 +1998,31 @@ class WebView extends View {
     return pigeonVar_replyValue as String?;
   }
 
+  /// Adds JavaScript that runs at the start of future document loads.
+  Future<ScriptHandler> addDocumentStartJavaScript(String javaScript) async {
+    final _PigeonInternalProxyApiBaseCodec pigeonChannelCodec = _pigeonVar_codecWebView;
+    final BinaryMessenger? pigeonVar_binaryMessenger = pigeon_binaryMessenger;
+    const pigeonVar_channelName =
+        'dev.flutter.pigeon.webview_flutter_android.WebView.addDocumentStartJavaScript';
+    final pigeonVar_channel = BasicMessageChannel<Object?>(
+      pigeonVar_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: pigeonVar_binaryMessenger,
+    );
+    final Future<Object?> pigeonVar_sendFuture = pigeonVar_channel.send(<Object?>[
+      this,
+      javaScript,
+    ]);
+    final pigeonVar_replyList = await pigeonVar_sendFuture as List<Object?>?;
+
+    final Object? pigeonVar_replyValue = _extractReplyValueOrThrow(
+      pigeonVar_replyList,
+      pigeonVar_channelName,
+      isNullValid: false,
+    );
+    return pigeonVar_replyValue! as ScriptHandler;
+  }
+
   /// Gets the title for the current page.
   Future<String?> getTitle() async {
     final _PigeonInternalProxyApiBaseCodec pigeonChannelCodec = _pigeonVar_codecWebView;
@@ -7326,3 +7352,87 @@ class WebViewFeature extends PigeonInternalProxyApiBaseClass {
     );
   }
 }
+
+/// Handle to a document start JavaScript that was added with
+/// `WebView.addDocumentStartJavaScript`.
+///
+/// See https://developer.android.com/reference/kotlin/androidx/webkit/ScriptHandler.
+class ScriptHandler extends PigeonInternalProxyApiBaseClass {
+  /// Constructs [ScriptHandler] without creating the associated native object.
+  ///
+  /// This should only be used by subclasses created by this library or to
+  /// create copies for an [PigeonInstanceManager].
+  @protected
+  ScriptHandler.pigeon_detached({super.pigeon_binaryMessenger, super.pigeon_instanceManager});
+
+  late final _PigeonInternalProxyApiBaseCodec _pigeonVar_codecScriptHandler =
+      _PigeonInternalProxyApiBaseCodec(pigeon_instanceManager);
+
+  static void pigeon_setUpMessageHandlers({
+    bool pigeon_clearHandlers = false,
+    BinaryMessenger? pigeon_binaryMessenger,
+    PigeonInstanceManager? pigeon_instanceManager,
+    ScriptHandler Function()? pigeon_newInstance,
+  }) {
+    final _PigeonInternalProxyApiBaseCodec pigeonChannelCodec = _PigeonInternalProxyApiBaseCodec(
+      pigeon_instanceManager ?? PigeonInstanceManager.instance,
+    );
+    final BinaryMessenger? binaryMessenger = pigeon_binaryMessenger;
+    {
+      final pigeonVar_channel = BasicMessageChannel<Object?>(
+        'dev.flutter.pigeon.webview_flutter_android.ScriptHandler.pigeon_newInstance',
+        pigeonChannelCodec,
+        binaryMessenger: binaryMessenger,
+      );
+      if (pigeon_clearHandlers) {
+        pigeonVar_channel.setMessageHandler(null);
+      } else {
+        pigeonVar_channel.setMessageHandler((Object? message) async {
+          final List<Object?> args = message! as List<Object?>;
+          final int arg_pigeon_instanceIdentifier = args[0]! as int;
+          try {
+            (pigeon_instanceManager ?? PigeonInstanceManager.instance).addHostCreatedInstance(
+              pigeon_newInstance?.call() ??
+                  ScriptHandler.pigeon_detached(
+                    pigeon_binaryMessenger: pigeon_binaryMessenger,
+                    pigeon_instanceManager: pigeon_instanceManager,
+                  ),
+              arg_pigeon_instanceIdentifier,
+            );
+            return wrapResponse(empty: true);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+              error: PlatformException(code: 'error', message: e.toString()),
+            );
+          }
+        });
+      }
+    }
+  }
+
+  /// Removes the script from the WebView.
+  Future<void> remove() async {
+    final _PigeonInternalProxyApiBaseCodec pigeonChannelCodec = _pigeonVar_codecScriptHandler;
+    final BinaryMessenger? pigeonVar_binaryMessenger = pigeon_binaryMessenger;
+    const pigeonVar_channelName = 'dev.flutter.pigeon.webview_flutter_android.ScriptHandler.remove';
+    final pigeonVar_channel = BasicMessageChannel<Object?>(
+      pigeonVar_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: pigeonVar_binaryMessenger,
+    );
+    final Future<Object?> pigeonVar_sendFuture = pigeonVar_channel.send(<Object?>[this]);
+    final pigeonVar_replyList = await pigeonVar_sendFuture as List<Object?>?;
+
+    _extractReplyValueOrThrow(pigeonVar_replyList, pigeonVar_channelName, isNullValid: true);
+  }
+
+  @override
+  ScriptHandler pigeon_copy() {
+    return ScriptHandler.pigeon_detached(
+      pigeon_binaryMessenger: pigeon_binaryMessenger,
+      pigeon_instanceManager: pigeon_instanceManager,
+    );
+  }
+}
diff --git a/packages/webview_flutter/webview_flutter_android/lib/src/android_webkit_constants.dart b/packages/webview_flutter/webview_flutter_android/lib/src/android_webkit_constants.dart
index 5760d088bd6a..778d5d53afdc 100644
--- a/packages/webview_flutter/webview_flutter_android/lib/src/android_webkit_constants.dart
+++ b/packages/webview_flutter/webview_flutter_android/lib/src/android_webkit_constants.dart
@@ -131,4 +131,9 @@ class WebViewFeatureConstants {
   ///
   /// See https://developer.android.com/reference/androidx/webkit/WebViewFeature#WEB_AUTHENTICATION.
   static const String webAuthentication = 'WEB_AUTHENTICATION';
+
+  /// This feature covers [WebView.addDocumentStartJavaScript].
+  ///
+  /// See https://developer.android.com/reference/androidx/webkit/WebViewFeature#DOCUMENT_START_SCRIPT.
+  static const String documentStartScript = 'DOCUMENT_START_SCRIPT';
 }
diff --git a/packages/webview_flutter/webview_flutter_android/lib/src/android_webview_controller.dart b/packages/webview_flutter/webview_flutter_android/lib/src/android_webview_controller.dart
index e654baac8c9e..c143121a0664 100644
--- a/packages/webview_flutter/webview_flutter_android/lib/src/android_webview_controller.dart
+++ b/packages/webview_flutter/webview_flutter_android/lib/src/android_webview_controller.dart
@@ -518,6 +518,31 @@ class AndroidWebViewController extends PlatformWebViewController {
     return _webView.evaluateJavascript(javaScript);
   }
 
+  /// Adds JavaScript that runs at the start of future document loads.
+  ///
+  /// This requires the `DOCUMENT_START_SCRIPT` feature, which depends on the
+  /// version of the WebView installed on the device. Throws an
+  /// [UnsupportedError] if the feature is not available; support can be checked
+  /// ahead of time with [isWebViewFeatureSupported] and
+  /// [WebViewFeatureType.documentStartScript].
+  @override
+  Future<PlatformDocumentStartJavaScriptRegistration> addDocumentStartJavaScript(
+    String javaScript,
+  ) async {
+    final bool isSupported = await isWebViewFeatureSupported(
+      WebViewFeatureType.documentStartScript,
+    );
+    if (!isSupported) {
+      throw UnsupportedError(
+        'Document-start JavaScript injection is not supported by the WebView '
+        'installed on this device.',
+      );
+    }
+    return AndroidDocumentStartJavaScriptRegistration._(
+      await _webView.addDocumentStartJavaScript(javaScript),
+    );
+  }
+
   @override
   Future<Object> runJavaScriptReturningResult(String javaScript) async {
     final String? result = await _webView.evaluateJavascript(javaScript);
@@ -791,6 +816,7 @@ class AndroidWebViewController extends PlatformWebViewController {
     final String feature = switch (featureType) {
       WebViewFeatureType.paymentRequest => WebViewFeatureConstants.paymentRequest,
       WebViewFeatureType.webAuthentication => WebViewFeatureConstants.webAuthentication,
+      WebViewFeatureType.documentStartScript => WebViewFeatureConstants.documentStartScript,
     };
     return android_webview.WebViewFeature.isFeatureSupported(feature);
   }
@@ -997,6 +1023,9 @@ enum WebViewFeatureType {
   ///
   /// This feature covers [WebSettingsCompat.setWebAuthenticationSupport].
   webAuthentication,
+  /// This feature covers
+  /// [AndroidWebViewController.addDocumentStartJavaScript].
+  documentStartScript,
 }
 
 /// Support levels for [android_webview.WebSettingsCompat.setWebAuthenticationSupport].
@@ -1076,6 +1105,28 @@ class FileSelectorParams {
   final FileSelectorMode mode;
 }
 
+/// An implementation of [PlatformDocumentStartJavaScriptRegistration] with the Android
+/// WebView API.
+///
+/// See [AndroidWebViewController.addDocumentStartJavaScript].
+class AndroidDocumentStartJavaScriptRegistration
+    extends PlatformDocumentStartJavaScriptRegistration {
+  AndroidDocumentStartJavaScriptRegistration._(this._scriptHandler);
+
+  final android_webview.ScriptHandler _scriptHandler;
+
+  bool _removed = false;
+
+  @override
+  Future<void> remove() async {
+    if (_removed) {
+      return;
+    }
+    _removed = true;
+    await _scriptHandler.remove();
+  }
+}
+
 /// An implementation of [JavaScriptChannelParams] with the Android WebView API.
 ///
 /// See [AndroidWebViewController.addJavaScriptChannel].
diff --git a/packages/webview_flutter/webview_flutter_android/pigeons/android_webkit.dart b/packages/webview_flutter/webview_flutter_android/pigeons/android_webkit.dart
index 5ed5a57fd72c..8a7829d11276 100644
--- a/packages/webview_flutter/webview_flutter_android/pigeons/android_webkit.dart
+++ b/packages/webview_flutter/webview_flutter_android/pigeons/android_webkit.dart
@@ -347,6 +347,9 @@ abstract class WebView extends View {
   @async
   String? evaluateJavascript(String javascriptString);
 
+  /// Adds JavaScript that runs at the start of future document loads.
+  ScriptHandler addDocumentStartJavaScript(String javaScript);
+
   /// Gets the title for the current page.
   String? getTitle();
 
@@ -1017,3 +1020,13 @@ abstract class WebViewFeature {
   @static
   bool isFeatureSupported(String feature);
 }
+
+/// Handle to a document start JavaScript that was added with
+/// `WebView.addDocumentStartJavaScript`.
+///
+/// See https://developer.android.com/reference/kotlin/androidx/webkit/ScriptHandler.
+@ProxyApi(kotlinOptions: KotlinProxyApiOptions(fullClassName: 'androidx.webkit.ScriptHandler'))
+abstract class ScriptHandler {
+  /// Removes the script from the WebView.
+  void remove();
+}
diff --git a/packages/webview_flutter/webview_flutter_android/pubspec.yaml b/packages/webview_flutter/webview_flutter_android/pubspec.yaml
index 7b5d83779c7a..0dcf930353a3 100644
--- a/packages/webview_flutter/webview_flutter_android/pubspec.yaml
+++ b/packages/webview_flutter/webview_flutter_android/pubspec.yaml
@@ -2,7 +2,7 @@ name: webview_flutter_android
 description: A Flutter plugin that provides a WebView widget on Android.
 repository: https://github.com/flutter/packages/tree/main/packages/webview_flutter/webview_flutter_android
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+webview%22
-version: 4.14.0
+version: 4.15.0
 
 environment:
   sdk: ^3.12.0
@@ -21,7 +21,7 @@ dependencies:
   flutter:
     sdk: flutter
   meta: ^1.10.0
-  webview_flutter_platform_interface: ^2.15.1
+  webview_flutter_platform_interface: ^2.16.0
 
 dev_dependencies:
   build_runner: ^2.1.4
diff --git a/packages/webview_flutter/webview_flutter_android/test/android_webview_controller_test.dart b/packages/webview_flutter/webview_flutter_android/test/android_webview_controller_test.dart
index 8808866aad31..31b0a4c4ef84 100644
--- a/packages/webview_flutter/webview_flutter_android/test/android_webview_controller_test.dart
+++ b/packages/webview_flutter/webview_flutter_android/test/android_webview_controller_test.dart
@@ -26,6 +26,7 @@ import 'android_webview_controller_test.mocks.dart';
   MockSpec<android_webview.JavaScriptChannel>(),
   MockSpec<android_webview.PermissionRequest>(),
   MockSpec<PlatformViewsServiceProxy>(),
+  MockSpec<android_webview.ScriptHandler>(),
   MockSpec<SurfaceAndroidViewController>(),
   MockSpec<android_webview.WebChromeClient>(),
   MockSpec<android_webview.WebSettings>(),
@@ -1406,6 +1407,68 @@ void main() {
       verify(mockWebView.evaluateJavascript('alert("This is a test.");')).called(1);
     });
 
+    test('addDocumentStartJavaScript', () async {
+      final mockWebView = MockWebView();
+      final mockScriptHandler = MockScriptHandler();
+      final AndroidWebViewController controller = createControllerWithMocks(
+        mockWebView: mockWebView,
+        isWebViewFeatureSupported: (_) async => true,
+      );
+      when(mockWebView.addDocumentStartJavaScript(any)).thenAnswer((_) async => mockScriptHandler);
+
+      await controller.addDocumentStartJavaScript('window.test = true;');
+
+      verify(mockWebView.addDocumentStartJavaScript('window.test = true;')).called(1);
+    });
+
+    test('addDocumentStartJavaScript throws if the feature is unsupported', () async {
+      final mockWebView = MockWebView();
+      final AndroidWebViewController controller = createControllerWithMocks(
+        mockWebView: mockWebView,
+        isWebViewFeatureSupported: (_) async => false,
+      );
+
+      await expectLater(
+        () => controller.addDocumentStartJavaScript('window.test = true;'),
+        throwsA(isA<UnsupportedError>()),
+      );
+
+      verifyNever(mockWebView.addDocumentStartJavaScript(any));
+    });
+
+    test('removing document start JavaScript removes the script handler', () async {
+      final mockWebView = MockWebView();
+      final mockScriptHandler = MockScriptHandler();
+      final AndroidWebViewController controller = createControllerWithMocks(
+        mockWebView: mockWebView,
+        isWebViewFeatureSupported: (_) async => true,
+      );
+      when(mockWebView.addDocumentStartJavaScript(any)).thenAnswer((_) async => mockScriptHandler);
+
+      final PlatformDocumentStartJavaScriptRegistration documentStartJavaScript = await controller
+          .addDocumentStartJavaScript('window.test = true;');
+      await documentStartJavaScript.remove();
+
+      verify(mockScriptHandler.remove()).called(1);
+    });
+
+    test('removing document start JavaScript more than once is a no-op', () async {
+      final mockWebView = MockWebView();
+      final mockScriptHandler = MockScriptHandler();
+      final AndroidWebViewController controller = createControllerWithMocks(
+        mockWebView: mockWebView,
+        isWebViewFeatureSupported: (_) async => true,
+      );
+      when(mockWebView.addDocumentStartJavaScript(any)).thenAnswer((_) async => mockScriptHandler);
+
+      final PlatformDocumentStartJavaScriptRegistration documentStartJavaScript = await controller
+          .addDocumentStartJavaScript('window.test = true;');
+      await documentStartJavaScript.remove();
+      await documentStartJavaScript.remove();
+
+      verify(mockScriptHandler.remove()).called(1);
+    });
+
     test('runJavaScriptReturningResult with return value', () async {
       final mockWebView = MockWebView();
       final AndroidWebViewController controller = createControllerWithMocks(
diff --git a/packages/webview_flutter/webview_flutter_android/test/android_webview_controller_test.mocks.dart b/packages/webview_flutter/webview_flutter_android/test/android_webview_controller_test.mocks.dart
index c4c72286f5b2..3d6210edb426 100644
--- a/packages/webview_flutter/webview_flutter_android/test/android_webview_controller_test.mocks.dart
+++ b/packages/webview_flutter/webview_flutter_android/test/android_webview_controller_test.mocks.dart
@@ -59,83 +59,94 @@ class _FakePlatformWebViewControllerCreationParams_4 extends _i1.SmartFake
     : super(parent, parentInvocation);
 }
 
-class _FakeObject_5 extends _i1.SmartFake implements Object {
-  _FakeObject_5(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakePlatformDocumentStartJavaScript_5 extends _i1.SmartFake
+    implements _i3.PlatformDocumentStartJavaScriptRegistration {
+  _FakePlatformDocumentStartJavaScript_5(Object parent, Invocation parentInvocation)
+    : super(parent, parentInvocation);
+}
+
+class _FakeObject_6 extends _i1.SmartFake implements Object {
+  _FakeObject_6(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
-class _FakeOffset_6 extends _i1.SmartFake implements _i4.Offset {
-  _FakeOffset_6(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakeOffset_7 extends _i1.SmartFake implements _i4.Offset {
+  _FakeOffset_7(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
-class _FakePlatformViewsServiceProxy_7 extends _i1.SmartFake
+class _FakePlatformViewsServiceProxy_8 extends _i1.SmartFake
     implements _i5.PlatformViewsServiceProxy {
-  _FakePlatformViewsServiceProxy_7(Object parent, Invocation parentInvocation)
+  _FakePlatformViewsServiceProxy_8(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakePlatformWebViewController_8 extends _i1.SmartFake
+class _FakePlatformWebViewController_9 extends _i1.SmartFake
     implements _i3.PlatformWebViewController {
-  _FakePlatformWebViewController_8(Object parent, Invocation parentInvocation)
+  _FakePlatformWebViewController_9(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeSize_9 extends _i1.SmartFake implements _i4.Size {
-  _FakeSize_9(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakeSize_10 extends _i1.SmartFake implements _i4.Size {
+  _FakeSize_10(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
-class _FakePigeonInstanceManager_10 extends _i1.SmartFake implements _i2.PigeonInstanceManager {
-  _FakePigeonInstanceManager_10(Object parent, Invocation parentInvocation)
+class _FakePigeonInstanceManager_11 extends _i1.SmartFake implements _i2.PigeonInstanceManager {
+  _FakePigeonInstanceManager_11(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeFlutterAssetManager_11 extends _i1.SmartFake implements _i2.FlutterAssetManager {
-  _FakeFlutterAssetManager_11(Object parent, Invocation parentInvocation)
+class _FakeFlutterAssetManager_12 extends _i1.SmartFake implements _i2.FlutterAssetManager {
+  _FakeFlutterAssetManager_12(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeGeolocationPermissionsCallback_12 extends _i1.SmartFake
+class _FakeGeolocationPermissionsCallback_13 extends _i1.SmartFake
     implements _i2.GeolocationPermissionsCallback {
-  _FakeGeolocationPermissionsCallback_12(Object parent, Invocation parentInvocation)
+  _FakeGeolocationPermissionsCallback_13(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeJavaScriptChannel_13 extends _i1.SmartFake implements _i2.JavaScriptChannel {
-  _FakeJavaScriptChannel_13(Object parent, Invocation parentInvocation)
+class _FakeJavaScriptChannel_14 extends _i1.SmartFake implements _i2.JavaScriptChannel {
+  _FakeJavaScriptChannel_14(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakePermissionRequest_14 extends _i1.SmartFake implements _i2.PermissionRequest {
-  _FakePermissionRequest_14(Object parent, Invocation parentInvocation)
+class _FakePermissionRequest_15 extends _i1.SmartFake implements _i2.PermissionRequest {
+  _FakePermissionRequest_15(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeExpensiveAndroidViewController_15 extends _i1.SmartFake
+class _FakeExpensiveAndroidViewController_16 extends _i1.SmartFake
     implements _i6.ExpensiveAndroidViewController {
-  _FakeExpensiveAndroidViewController_15(Object parent, Invocation parentInvocation)
+  _FakeExpensiveAndroidViewController_16(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeSurfaceAndroidViewController_16 extends _i1.SmartFake
+class _FakeSurfaceAndroidViewController_17 extends _i1.SmartFake
     implements _i6.SurfaceAndroidViewController {
-  _FakeSurfaceAndroidViewController_16(Object parent, Invocation parentInvocation)
+  _FakeSurfaceAndroidViewController_17(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeWebSettings_17 extends _i1.SmartFake implements _i2.WebSettings {
-  _FakeWebSettings_17(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakeScriptHandler_18 extends _i1.SmartFake implements _i2.ScriptHandler {
+  _FakeScriptHandler_18(Object parent, Invocation parentInvocation)
+    : super(parent, parentInvocation);
 }
 
-class _FakeWebView_18 extends _i1.SmartFake implements _i2.WebView {
-  _FakeWebView_18(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakeWebSettings_19 extends _i1.SmartFake implements _i2.WebSettings {
+  _FakeWebSettings_19(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
-class _FakeWebViewPoint_19 extends _i1.SmartFake implements _i2.WebViewPoint {
-  _FakeWebViewPoint_19(Object parent, Invocation parentInvocation)
+class _FakeWebView_20 extends _i1.SmartFake implements _i2.WebView {
+  _FakeWebView_20(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+}
+
+class _FakeWebViewPoint_21 extends _i1.SmartFake implements _i2.WebViewPoint {
+  _FakeWebViewPoint_21(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeWebStorage_20 extends _i1.SmartFake implements _i2.WebStorage {
-  _FakeWebStorage_20(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakeWebStorage_22 extends _i1.SmartFake implements _i2.WebStorage {
+  _FakeWebStorage_22(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
 /// A class which mocks [AndroidNavigationDelegate].
@@ -456,15 +467,37 @@ class MockAndroidWebViewController extends _i1.Mock implements _i7.AndroidWebVie
           )
           as _i8.Future<void>);
 
+  @override
+  _i8.Future<_i3.PlatformDocumentStartJavaScriptRegistration> addDocumentStartJavaScript(
+    String? javaScript,
+  ) =>
+      (super.noSuchMethod(
+            Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+            returnValue: _i8.Future<_i3.PlatformDocumentStartJavaScriptRegistration>.value(
+              _FakePlatformDocumentStartJavaScript_5(
+                this,
+                Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+              ),
+            ),
+            returnValueForMissingStub:
+                _i8.Future<_i3.PlatformDocumentStartJavaScriptRegistration>.value(
+                  _FakePlatformDocumentStartJavaScript_5(
+                    this,
+                    Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+                  ),
+                ),
+          )
+          as _i8.Future<_i3.PlatformDocumentStartJavaScriptRegistration>);
+
   @override
   _i8.Future<Object> runJavaScriptReturningResult(String? javaScript) =>
       (super.noSuchMethod(
             Invocation.method(#runJavaScriptReturningResult, [javaScript]),
             returnValue: _i8.Future<Object>.value(
-              _FakeObject_5(this, Invocation.method(#runJavaScriptReturningResult, [javaScript])),
+              _FakeObject_6(this, Invocation.method(#runJavaScriptReturningResult, [javaScript])),
             ),
             returnValueForMissingStub: _i8.Future<Object>.value(
-              _FakeObject_5(this, Invocation.method(#runJavaScriptReturningResult, [javaScript])),
+              _FakeObject_6(this, Invocation.method(#runJavaScriptReturningResult, [javaScript])),
             ),
           )
           as _i8.Future<Object>);
@@ -519,10 +552,10 @@ class MockAndroidWebViewController extends _i1.Mock implements _i7.AndroidWebVie
       (super.noSuchMethod(
             Invocation.method(#getScrollPosition, []),
             returnValue: _i8.Future<_i4.Offset>.value(
-              _FakeOffset_6(this, Invocation.method(#getScrollPosition, [])),
+              _FakeOffset_7(this, Invocation.method(#getScrollPosition, [])),
             ),
             returnValueForMissingStub: _i8.Future<_i4.Offset>.value(
-              _FakeOffset_6(this, Invocation.method(#getScrollPosition, [])),
+              _FakeOffset_7(this, Invocation.method(#getScrollPosition, [])),
             ),
           )
           as _i8.Future<_i4.Offset>);
@@ -816,11 +849,11 @@ class MockAndroidWebViewWidgetCreationParams extends _i1.Mock
   _i5.PlatformViewsServiceProxy get platformViewsServiceProxy =>
       (super.noSuchMethod(
             Invocation.getter(#platformViewsServiceProxy),
-            returnValue: _FakePlatformViewsServiceProxy_7(
+            returnValue: _FakePlatformViewsServiceProxy_8(
               this,
               Invocation.getter(#platformViewsServiceProxy),
             ),
-            returnValueForMissingStub: _FakePlatformViewsServiceProxy_7(
+            returnValueForMissingStub: _FakePlatformViewsServiceProxy_8(
               this,
               Invocation.getter(#platformViewsServiceProxy),
             ),
@@ -840,8 +873,8 @@ class MockAndroidWebViewWidgetCreationParams extends _i1.Mock
   _i3.PlatformWebViewController get controller =>
       (super.noSuchMethod(
             Invocation.getter(#controller),
-            returnValue: _FakePlatformWebViewController_8(this, Invocation.getter(#controller)),
-            returnValueForMissingStub: _FakePlatformWebViewController_8(
+            returnValue: _FakePlatformWebViewController_9(this, Invocation.getter(#controller)),
+            returnValueForMissingStub: _FakePlatformWebViewController_9(
               this,
               Invocation.getter(#controller),
             ),
@@ -900,9 +933,9 @@ class MockExpensiveAndroidViewController extends _i1.Mock
       (super.noSuchMethod(
             Invocation.getter(#pointTransformer),
             returnValue: (_i4.Offset position) =>
-                _FakeOffset_6(this, Invocation.getter(#pointTransformer)),
+                _FakeOffset_7(this, Invocation.getter(#pointTransformer)),
             returnValueForMissingStub: (_i4.Offset position) =>
-                _FakeOffset_6(this, Invocation.getter(#pointTransformer)),
+                _FakeOffset_7(this, Invocation.getter(#pointTransformer)),
           )
           as _i6.PointTransformer);
 
@@ -953,10 +986,10 @@ class MockExpensiveAndroidViewController extends _i1.Mock
       (super.noSuchMethod(
             Invocation.method(#setSize, [size]),
             returnValue: _i8.Future<_i4.Size>.value(
-              _FakeSize_9(this, Invocation.method(#setSize, [size])),
+              _FakeSize_10(this, Invocation.method(#setSize, [size])),
             ),
             returnValueForMissingStub: _i8.Future<_i4.Size>.value(
-              _FakeSize_9(this, Invocation.method(#setSize, [size])),
+              _FakeSize_10(this, Invocation.method(#setSize, [size])),
             ),
           )
           as _i8.Future<_i4.Size>);
@@ -1029,11 +1062,11 @@ class MockFlutterAssetManager extends _i1.Mock implements _i2.FlutterAssetManage
   _i2.PigeonInstanceManager get pigeon_instanceManager =>
       (super.noSuchMethod(
             Invocation.getter(#pigeon_instanceManager),
-            returnValue: _FakePigeonInstanceManager_10(
+            returnValue: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
-            returnValueForMissingStub: _FakePigeonInstanceManager_10(
+            returnValueForMissingStub: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
@@ -1066,8 +1099,8 @@ class MockFlutterAssetManager extends _i1.Mock implements _i2.FlutterAssetManage
   _i2.FlutterAssetManager pigeon_copy() =>
       (super.noSuchMethod(
             Invocation.method(#pigeon_copy, []),
-            returnValue: _FakeFlutterAssetManager_11(this, Invocation.method(#pigeon_copy, [])),
-            returnValueForMissingStub: _FakeFlutterAssetManager_11(
+            returnValue: _FakeFlutterAssetManager_12(this, Invocation.method(#pigeon_copy, [])),
+            returnValueForMissingStub: _FakeFlutterAssetManager_12(
               this,
               Invocation.method(#pigeon_copy, []),
             ),
@@ -1084,11 +1117,11 @@ class MockGeolocationPermissionsCallback extends _i1.Mock
   _i2.PigeonInstanceManager get pigeon_instanceManager =>
       (super.noSuchMethod(
             Invocation.getter(#pigeon_instanceManager),
-            returnValue: _FakePigeonInstanceManager_10(
+            returnValue: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
-            returnValueForMissingStub: _FakePigeonInstanceManager_10(
+            returnValueForMissingStub: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
@@ -1108,11 +1141,11 @@ class MockGeolocationPermissionsCallback extends _i1.Mock
   _i2.GeolocationPermissionsCallback pigeon_copy() =>
       (super.noSuchMethod(
             Invocation.method(#pigeon_copy, []),
-            returnValue: _FakeGeolocationPermissionsCallback_12(
+            returnValue: _FakeGeolocationPermissionsCallback_13(
               this,
               Invocation.method(#pigeon_copy, []),
             ),
-            returnValueForMissingStub: _FakeGeolocationPermissionsCallback_12(
+            returnValueForMissingStub: _FakeGeolocationPermissionsCallback_13(
               this,
               Invocation.method(#pigeon_copy, []),
             ),
@@ -1149,11 +1182,11 @@ class MockJavaScriptChannel extends _i1.Mock implements _i2.JavaScriptChannel {
   _i2.PigeonInstanceManager get pigeon_instanceManager =>
       (super.noSuchMethod(
             Invocation.getter(#pigeon_instanceManager),
-            returnValue: _FakePigeonInstanceManager_10(
+            returnValue: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
-            returnValueForMissingStub: _FakePigeonInstanceManager_10(
+            returnValueForMissingStub: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
@@ -1164,8 +1197,8 @@ class MockJavaScriptChannel extends _i1.Mock implements _i2.JavaScriptChannel {
   _i2.JavaScriptChannel pigeon_copy() =>
       (super.noSuchMethod(
             Invocation.method(#pigeon_copy, []),
-            returnValue: _FakeJavaScriptChannel_13(this, Invocation.method(#pigeon_copy, [])),
-            returnValueForMissingStub: _FakeJavaScriptChannel_13(
+            returnValue: _FakeJavaScriptChannel_14(this, Invocation.method(#pigeon_copy, [])),
+            returnValueForMissingStub: _FakeJavaScriptChannel_14(
               this,
               Invocation.method(#pigeon_copy, []),
             ),
@@ -1190,11 +1223,11 @@ class MockPermissionRequest extends _i1.Mock implements _i2.PermissionRequest {
   _i2.PigeonInstanceManager get pigeon_instanceManager =>
       (super.noSuchMethod(
             Invocation.getter(#pigeon_instanceManager),
-            returnValue: _FakePigeonInstanceManager_10(
+            returnValue: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
-            returnValueForMissingStub: _FakePigeonInstanceManager_10(
+            returnValueForMissingStub: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
@@ -1223,8 +1256,8 @@ class MockPermissionRequest extends _i1.Mock implements _i2.PermissionRequest {
   _i2.PermissionRequest pigeon_copy() =>
       (super.noSuchMethod(
             Invocation.method(#pigeon_copy, []),
-            returnValue: _FakePermissionRequest_14(this, Invocation.method(#pigeon_copy, [])),
-            returnValueForMissingStub: _FakePermissionRequest_14(
+            returnValue: _FakePermissionRequest_15(this, Invocation.method(#pigeon_copy, [])),
+            returnValueForMissingStub: _FakePermissionRequest_15(
               this,
               Invocation.method(#pigeon_copy, []),
             ),
@@ -1255,7 +1288,7 @@ class MockPlatformViewsServiceProxy extends _i1.Mock implements _i5.PlatformView
               #creationParamsCodec: creationParamsCodec,
               #onFocus: onFocus,
             }),
-            returnValue: _FakeExpensiveAndroidViewController_15(
+            returnValue: _FakeExpensiveAndroidViewController_16(
               this,
               Invocation.method(#initExpensiveAndroidView, [], {
                 #id: id,
@@ -1266,7 +1299,7 @@ class MockPlatformViewsServiceProxy extends _i1.Mock implements _i5.PlatformView
                 #onFocus: onFocus,
               }),
             ),
-            returnValueForMissingStub: _FakeExpensiveAndroidViewController_15(
+            returnValueForMissingStub: _FakeExpensiveAndroidViewController_16(
               this,
               Invocation.method(#initExpensiveAndroidView, [], {
                 #id: id,
@@ -1298,7 +1331,7 @@ class MockPlatformViewsServiceProxy extends _i1.Mock implements _i5.PlatformView
               #creationParamsCodec: creationParamsCodec,
               #onFocus: onFocus,
             }),
-            returnValue: _FakeSurfaceAndroidViewController_16(
+            returnValue: _FakeSurfaceAndroidViewController_17(
               this,
               Invocation.method(#initSurfaceAndroidView, [], {
                 #id: id,
@@ -1309,7 +1342,7 @@ class MockPlatformViewsServiceProxy extends _i1.Mock implements _i5.PlatformView
                 #onFocus: onFocus,
               }),
             ),
-            returnValueForMissingStub: _FakeSurfaceAndroidViewController_16(
+            returnValueForMissingStub: _FakeSurfaceAndroidViewController_17(
               this,
               Invocation.method(#initSurfaceAndroidView, [], {
                 #id: id,
@@ -1324,6 +1357,47 @@ class MockPlatformViewsServiceProxy extends _i1.Mock implements _i5.PlatformView
           as _i6.SurfaceAndroidViewController);
 }
 
+/// A class which mocks [ScriptHandler].
+///
+/// See the documentation for Mockito's code generation for more information.
+class MockScriptHandler extends _i1.Mock implements _i2.ScriptHandler {
+  @override
+  _i2.PigeonInstanceManager get pigeon_instanceManager =>
+      (super.noSuchMethod(
+            Invocation.getter(#pigeon_instanceManager),
+            returnValue: _FakePigeonInstanceManager_11(
+              this,
+              Invocation.getter(#pigeon_instanceManager),
+            ),
+            returnValueForMissingStub: _FakePigeonInstanceManager_11(
+              this,
+              Invocation.getter(#pigeon_instanceManager),
+            ),
+          )
+          as _i2.PigeonInstanceManager);
+
+  @override
+  _i8.Future<void> remove() =>
+      (super.noSuchMethod(
+            Invocation.method(#remove, []),
+            returnValue: _i8.Future<void>.value(),
+            returnValueForMissingStub: _i8.Future<void>.value(),
+          )
+          as _i8.Future<void>);
+
+  @override
+  _i2.ScriptHandler pigeon_copy() =>
+      (super.noSuchMethod(
+            Invocation.method(#pigeon_copy, []),
+            returnValue: _FakeScriptHandler_18(this, Invocation.method(#pigeon_copy, [])),
+            returnValueForMissingStub: _FakeScriptHandler_18(
+              this,
+              Invocation.method(#pigeon_copy, []),
+            ),
+          )
+          as _i2.ScriptHandler);
+}
+
 /// A class which mocks [SurfaceAndroidViewController].
 ///
 /// See the documentation for Mockito's code generation for more information.
@@ -1357,9 +1431,9 @@ class MockSurfaceAndroidViewController extends _i1.Mock
       (super.noSuchMethod(
             Invocation.getter(#pointTransformer),
             returnValue: (_i4.Offset position) =>
-                _FakeOffset_6(this, Invocation.getter(#pointTransformer)),
+                _FakeOffset_7(this, Invocation.getter(#pointTransformer)),
             returnValueForMissingStub: (_i4.Offset position) =>
-                _FakeOffset_6(this, Invocation.getter(#pointTransformer)),
+                _FakeOffset_7(this, Invocation.getter(#pointTransformer)),
           )
           as _i6.PointTransformer);
 
@@ -1410,10 +1484,10 @@ class MockSurfaceAndroidViewController extends _i1.Mock
       (super.noSuchMethod(
             Invocation.method(#setSize, [size]),
             returnValue: _i8.Future<_i4.Size>.value(
-              _FakeSize_9(this, Invocation.method(#setSize, [size])),
+              _FakeSize_10(this, Invocation.method(#setSize, [size])),
             ),
             returnValueForMissingStub: _i8.Future<_i4.Size>.value(
-              _FakeSize_9(this, Invocation.method(#setSize, [size])),
+              _FakeSize_10(this, Invocation.method(#setSize, [size])),
             ),
           )
           as _i8.Future<_i4.Size>);
@@ -1531,11 +1605,11 @@ class MockWebChromeClient extends _i1.Mock implements _i2.WebChromeClient {
   _i2.PigeonInstanceManager get pigeon_instanceManager =>
       (super.noSuchMethod(
             Invocation.getter(#pigeon_instanceManager),
-            returnValue: _FakePigeonInstanceManager_10(
+            returnValue: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
-            returnValueForMissingStub: _FakePigeonInstanceManager_10(
+            returnValueForMissingStub: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
@@ -1608,11 +1682,11 @@ class MockWebSettings extends _i1.Mock implements _i2.WebSettings {
   _i2.PigeonInstanceManager get pigeon_instanceManager =>
       (super.noSuchMethod(
             Invocation.getter(#pigeon_instanceManager),
-            returnValue: _FakePigeonInstanceManager_10(
+            returnValue: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
-            returnValueForMissingStub: _FakePigeonInstanceManager_10(
+            returnValueForMissingStub: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
@@ -1780,8 +1854,8 @@ class MockWebSettings extends _i1.Mock implements _i2.WebSettings {
   _i2.WebSettings pigeon_copy() =>
       (super.noSuchMethod(
             Invocation.method(#pigeon_copy, []),
-            returnValue: _FakeWebSettings_17(this, Invocation.method(#pigeon_copy, [])),
-            returnValueForMissingStub: _FakeWebSettings_17(
+            returnValue: _FakeWebSettings_19(this, Invocation.method(#pigeon_copy, [])),
+            returnValueForMissingStub: _FakeWebSettings_19(
               this,
               Invocation.method(#pigeon_copy, []),
             ),
@@ -1797,8 +1871,8 @@ class MockWebView extends _i1.Mock implements _i2.WebView {
   _i2.WebSettings get settings =>
       (super.noSuchMethod(
             Invocation.getter(#settings),
-            returnValue: _FakeWebSettings_17(this, Invocation.getter(#settings)),
-            returnValueForMissingStub: _FakeWebSettings_17(this, Invocation.getter(#settings)),
+            returnValue: _FakeWebSettings_19(this, Invocation.getter(#settings)),
+            returnValueForMissingStub: _FakeWebSettings_19(this, Invocation.getter(#settings)),
           )
           as _i2.WebSettings);
 
@@ -1806,11 +1880,11 @@ class MockWebView extends _i1.Mock implements _i2.WebView {
   _i2.PigeonInstanceManager get pigeon_instanceManager =>
       (super.noSuchMethod(
             Invocation.getter(#pigeon_instanceManager),
-            returnValue: _FakePigeonInstanceManager_10(
+            returnValue: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
-            returnValueForMissingStub: _FakePigeonInstanceManager_10(
+            returnValueForMissingStub: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
@@ -1821,8 +1895,8 @@ class MockWebView extends _i1.Mock implements _i2.WebView {
   _i2.WebSettings pigeonVar_settings() =>
       (super.noSuchMethod(
             Invocation.method(#pigeonVar_settings, []),
-            returnValue: _FakeWebSettings_17(this, Invocation.method(#pigeonVar_settings, [])),
-            returnValueForMissingStub: _FakeWebSettings_17(
+            returnValue: _FakeWebSettings_19(this, Invocation.method(#pigeonVar_settings, [])),
+            returnValueForMissingStub: _FakeWebSettings_19(
               this,
               Invocation.method(#pigeonVar_settings, []),
             ),
@@ -1949,6 +2023,25 @@ class MockWebView extends _i1.Mock implements _i2.WebView {
           )
           as _i8.Future<String?>);
 
+  @override
+  _i8.Future<_i2.ScriptHandler> addDocumentStartJavaScript(String? javaScript) =>
+      (super.noSuchMethod(
+            Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+            returnValue: _i8.Future<_i2.ScriptHandler>.value(
+              _FakeScriptHandler_18(
+                this,
+                Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+              ),
+            ),
+            returnValueForMissingStub: _i8.Future<_i2.ScriptHandler>.value(
+              _FakeScriptHandler_18(
+                this,
+                Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+              ),
+            ),
+          )
+          as _i8.Future<_i2.ScriptHandler>);
+
   @override
   _i8.Future<String?> getTitle() =>
       (super.noSuchMethod(
@@ -2025,8 +2118,8 @@ class MockWebView extends _i1.Mock implements _i2.WebView {
   _i2.WebView pigeon_copy() =>
       (super.noSuchMethod(
             Invocation.method(#pigeon_copy, []),
-            returnValue: _FakeWebView_18(this, Invocation.method(#pigeon_copy, [])),
-            returnValueForMissingStub: _FakeWebView_18(this, Invocation.method(#pigeon_copy, [])),
+            returnValue: _FakeWebView_20(this, Invocation.method(#pigeon_copy, [])),
+            returnValueForMissingStub: _FakeWebView_20(this, Invocation.method(#pigeon_copy, [])),
           )
           as _i2.WebView);
 
@@ -2053,10 +2146,10 @@ class MockWebView extends _i1.Mock implements _i2.WebView {
       (super.noSuchMethod(
             Invocation.method(#getScrollPosition, []),
             returnValue: _i8.Future<_i2.WebViewPoint>.value(
-              _FakeWebViewPoint_19(this, Invocation.method(#getScrollPosition, [])),
+              _FakeWebViewPoint_21(this, Invocation.method(#getScrollPosition, [])),
             ),
             returnValueForMissingStub: _i8.Future<_i2.WebViewPoint>.value(
-              _FakeWebViewPoint_19(this, Invocation.method(#getScrollPosition, [])),
+              _FakeWebViewPoint_21(this, Invocation.method(#getScrollPosition, [])),
             ),
           )
           as _i8.Future<_i2.WebViewPoint>);
@@ -2106,11 +2199,11 @@ class MockWebViewClient extends _i1.Mock implements _i2.WebViewClient {
   _i2.PigeonInstanceManager get pigeon_instanceManager =>
       (super.noSuchMethod(
             Invocation.getter(#pigeon_instanceManager),
-            returnValue: _FakePigeonInstanceManager_10(
+            returnValue: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
-            returnValueForMissingStub: _FakePigeonInstanceManager_10(
+            returnValueForMissingStub: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
@@ -2147,11 +2240,11 @@ class MockWebStorage extends _i1.Mock implements _i2.WebStorage {
   _i2.PigeonInstanceManager get pigeon_instanceManager =>
       (super.noSuchMethod(
             Invocation.getter(#pigeon_instanceManager),
-            returnValue: _FakePigeonInstanceManager_10(
+            returnValue: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
-            returnValueForMissingStub: _FakePigeonInstanceManager_10(
+            returnValueForMissingStub: _FakePigeonInstanceManager_11(
               this,
               Invocation.getter(#pigeon_instanceManager),
             ),
@@ -2171,8 +2264,8 @@ class MockWebStorage extends _i1.Mock implements _i2.WebStorage {
   _i2.WebStorage pigeon_copy() =>
       (super.noSuchMethod(
             Invocation.method(#pigeon_copy, []),
-            returnValue: _FakeWebStorage_20(this, Invocation.method(#pigeon_copy, [])),
-            returnValueForMissingStub: _FakeWebStorage_20(
+            returnValue: _FakeWebStorage_22(this, Invocation.method(#pigeon_copy, [])),
+            returnValueForMissingStub: _FakeWebStorage_22(
               this,
               Invocation.method(#pigeon_copy, []),
             ),
diff --git a/packages/webview_flutter/webview_flutter_android/test/android_webview_cookie_manager_test.mocks.dart b/packages/webview_flutter/webview_flutter_android/test/android_webview_cookie_manager_test.mocks.dart
index 12e125135c23..44db4802868e 100644
--- a/packages/webview_flutter/webview_flutter_android/test/android_webview_cookie_manager_test.mocks.dart
+++ b/packages/webview_flutter/webview_flutter_android/test/android_webview_cookie_manager_test.mocks.dart
@@ -42,12 +42,18 @@ class _FakePlatformWebViewControllerCreationParams_2 extends _i1.SmartFake
     : super(parent, parentInvocation);
 }
 
-class _FakeObject_3 extends _i1.SmartFake implements Object {
-  _FakeObject_3(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakePlatformDocumentStartJavaScript_3 extends _i1.SmartFake
+    implements _i3.PlatformDocumentStartJavaScriptRegistration {
+  _FakePlatformDocumentStartJavaScript_3(Object parent, Invocation parentInvocation)
+    : super(parent, parentInvocation);
+}
+
+class _FakeObject_4 extends _i1.SmartFake implements Object {
+  _FakeObject_4(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
-class _FakeOffset_4 extends _i1.SmartFake implements _i4.Offset {
-  _FakeOffset_4(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakeOffset_5 extends _i1.SmartFake implements _i4.Offset {
+  _FakeOffset_5(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
 /// A class which mocks [CookieManager].
@@ -276,12 +282,27 @@ class MockAndroidWebViewController extends _i1.Mock implements _i6.AndroidWebVie
           )
           as _i5.Future<void>);
 
+  @override
+  _i5.Future<_i3.PlatformDocumentStartJavaScriptRegistration> addDocumentStartJavaScript(
+    String? javaScript,
+  ) =>
+      (super.noSuchMethod(
+            Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+            returnValue: _i5.Future<_i3.PlatformDocumentStartJavaScriptRegistration>.value(
+              _FakePlatformDocumentStartJavaScript_3(
+                this,
+                Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+              ),
+            ),
+          )
+          as _i5.Future<_i3.PlatformDocumentStartJavaScriptRegistration>);
+
   @override
   _i5.Future<Object> runJavaScriptReturningResult(String? javaScript) =>
       (super.noSuchMethod(
             Invocation.method(#runJavaScriptReturningResult, [javaScript]),
             returnValue: _i5.Future<Object>.value(
-              _FakeObject_3(this, Invocation.method(#runJavaScriptReturningResult, [javaScript])),
+              _FakeObject_4(this, Invocation.method(#runJavaScriptReturningResult, [javaScript])),
             ),
           )
           as _i5.Future<Object>);
@@ -335,7 +356,7 @@ class MockAndroidWebViewController extends _i1.Mock implements _i6.AndroidWebVie
       (super.noSuchMethod(
             Invocation.method(#getScrollPosition, []),
             returnValue: _i5.Future<_i4.Offset>.value(
-              _FakeOffset_4(this, Invocation.method(#getScrollPosition, [])),
+              _FakeOffset_5(this, Invocation.method(#getScrollPosition, [])),
             ),
           )
           as _i5.Future<_i4.Offset>);
diff --git a/packages/webview_flutter/webview_flutter_android/test/legacy/webview_android_widget_test.mocks.dart b/packages/webview_flutter/webview_flutter_android/test/legacy/webview_android_widget_test.mocks.dart
index a2928df0253d..62d29024520a 100644
--- a/packages/webview_flutter/webview_flutter_android/test/legacy/webview_android_widget_test.mocks.dart
+++ b/packages/webview_flutter/webview_flutter_android/test/legacy/webview_android_widget_test.mocks.dart
@@ -46,42 +46,47 @@ class _FakeWebStorage_3 extends _i1.SmartFake implements _i2.WebStorage {
   _FakeWebStorage_3(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
-class _FakeWebView_4 extends _i1.SmartFake implements _i2.WebView {
-  _FakeWebView_4(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakeScriptHandler_4 extends _i1.SmartFake implements _i2.ScriptHandler {
+  _FakeScriptHandler_4(Object parent, Invocation parentInvocation)
+    : super(parent, parentInvocation);
+}
+
+class _FakeWebView_5 extends _i1.SmartFake implements _i2.WebView {
+  _FakeWebView_5(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
-class _FakeWebViewPoint_5 extends _i1.SmartFake implements _i2.WebViewPoint {
-  _FakeWebViewPoint_5(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
+class _FakeWebViewPoint_6 extends _i1.SmartFake implements _i2.WebViewPoint {
+  _FakeWebViewPoint_6(Object parent, Invocation parentInvocation) : super(parent, parentInvocation);
 }
 
-class _FakeWebResourceRequest_6 extends _i1.SmartFake implements _i2.WebResourceRequest {
-  _FakeWebResourceRequest_6(Object parent, Invocation parentInvocation)
+class _FakeWebResourceRequest_7 extends _i1.SmartFake implements _i2.WebResourceRequest {
+  _FakeWebResourceRequest_7(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeDownloadListener_7 extends _i1.SmartFake implements _i2.DownloadListener {
-  _FakeDownloadListener_7(Object parent, Invocation parentInvocation)
+class _FakeDownloadListener_8 extends _i1.SmartFake implements _i2.DownloadListener {
+  _FakeDownloadListener_8(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeJavascriptChannelRegistry_8 extends _i1.SmartFake
+class _FakeJavascriptChannelRegistry_9 extends _i1.SmartFake
     implements _i3.JavascriptChannelRegistry {
-  _FakeJavascriptChannelRegistry_8(Object parent, Invocation parentInvocation)
+  _FakeJavascriptChannelRegistry_9(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeJavaScriptChannel_9 extends _i1.SmartFake implements _i2.JavaScriptChannel {
-  _FakeJavaScriptChannel_9(Object parent, Invocation parentInvocation)
+class _FakeJavaScriptChannel_10 extends _i1.SmartFake implements _i2.JavaScriptChannel {
+  _FakeJavaScriptChannel_10(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeWebChromeClient_10 extends _i1.SmartFake implements _i2.WebChromeClient {
-  _FakeWebChromeClient_10(Object parent, Invocation parentInvocation)
+class _FakeWebChromeClient_11 extends _i1.SmartFake implements _i2.WebChromeClient {
+  _FakeWebChromeClient_11(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
-class _FakeWebViewClient_11 extends _i1.SmartFake implements _i2.WebViewClient {
-  _FakeWebViewClient_11(Object parent, Invocation parentInvocation)
+class _FakeWebViewClient_12 extends _i1.SmartFake implements _i2.WebViewClient {
+  _FakeWebViewClient_12(Object parent, Invocation parentInvocation)
     : super(parent, parentInvocation);
 }
 
@@ -498,6 +503,19 @@ class MockWebView extends _i1.Mock implements _i2.WebView {
           )
           as _i4.Future<String?>);
 
+  @override
+  _i4.Future<_i2.ScriptHandler> addDocumentStartJavaScript(String? javaScript) =>
+      (super.noSuchMethod(
+            Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+            returnValue: _i4.Future<_i2.ScriptHandler>.value(
+              _FakeScriptHandler_4(
+                this,
+                Invocation.method(#addDocumentStartJavaScript, [javaScript]),
+              ),
+            ),
+          )
+          as _i4.Future<_i2.ScriptHandler>);
+
   @override
   _i4.Future<String?> getTitle() =>
       (super.noSuchMethod(
@@ -573,7 +591,7 @@ class MockWebView extends _i1.Mock implements _i2.WebView {
   _i2.WebView pigeon_copy() =>
       (super.noSuchMethod(
             Invocation.method(#pigeon_copy, []),
-            returnValue: _FakeWebView_4(this, Invocation.method(#pigeon_copy, [])),
+            returnValue: _FakeWebView_5(this, Invocation.method(#pigeon_copy, [])),
           )
           as _i2.WebView);
 
@@ -600,7 +618,7 @@ class MockWebView extends _i1.Mock implements _i2.WebView {
       (super.noSuchMethod(
             Invocation.method(#getScrollPosition, []),
             returnValue: _i4.Future<_i2.WebViewPoint>.value(
-              _FakeWebViewPoint_5(this, Invocation.method(#getScrollPosition, [])),
+              _FakeWebViewPoint_6(this, Invocation.method(#getScrollPosition, [])),
             ),
           )
           as _i4.Future<_i2.WebViewPoint>);
@@ -693,7 +711,7 @@ class MockWebResourceRequest extends _i1.Mock implements _i2.WebResourceRequest
   _i2.WebResourceRequest pigeon_copy() =>
       (super.noSuchMethod(
             Invocation.method(#pigeon_copy, []),
-            returnValue: _FakeWebResourceRequest_6(this, Invocation.method(#pigeon_copy, [])),
+            returnValue: _FakeWebResourceRequest_7(this, Invocation.method(#pigeon_copy, [])),
           )
           as _i2.WebResourceRequest);
 }
@@ -737,7 +755,7 @@ class MockDownloadListener extends _i1.Mock implements _i2.DownloadListener {
   _i2.DownloadListener pigeon_copy() =>
       (super.noSuchMethod(
             Invocation.method(#pigeon_copy, []),
-            returnValue: _FakeDownloadListener_7(this, Invocation.method(#pigeon_copy, [])),
+            returnValue: _FakeDownloadListener_8(this, Invocation.method(#pigeon_copy, [])),
           )
           as _i2.DownloadListener);
 }
@@ -755,7 +773,7 @@ class MockWebViewAndroidJavaScriptChannel extends _i1.Mock
   _i3.JavascriptChannelRegistry get javascriptChannelRegistry =>
       (super.noSuchMethod(
             Invocation.getter(#javascriptChannelRegistry),
-            returnValue: _FakeJavascriptChannelRegistry_8(
+            returnValue: _FakeJavascriptChannelRegistry_9(
               this,
               Invocation.getter(#javascriptChannelRegistry),
             ),
@@ -793,7 +811,7 @@ class MockWebViewAndroidJavaScriptChannel extends _i1.Mock
   _i2.JavaScriptChannel pigeon_copy() =>
       (super.noSuchMethod(
             Invocation.method(#pigeon_copy, []),
-            returnValue: _FakeJavaScriptChannel_9(this, Invocation.method(#pigeon_copy, [])),
+            returnValue: _FakeJavaScriptChannel_10(this, Invocation.method(#pigeon_copy, [])),
           )
           as _i2.JavaScriptChannel);
 }
@@ -898,7 +916,7 @@ class MockWebChromeClient extends _i1.Mock implements _i2.WebChromeClient {
   _i2.WebChromeClient pigeon_copy() =>
       (super.noSuchMethod(
             Invocation.method(#pigeon_copy, []),
-            returnValue: _FakeWebChromeClient_10(this, Invocation.method(#pigeon_copy, [])),
+            returnValue: _FakeWebChromeClient_11(this, Invocation.method(#pigeon_copy, [])),
           )
           as _i2.WebChromeClient);
 }
@@ -935,7 +953,7 @@ class MockWebViewClient extends _i1.Mock implements _i2.WebViewClient {
   _i2.WebViewClient pigeon_copy() =>
       (super.noSuchMethod(
             Invocation.method(#pigeon_copy, []),
-            returnValue: _FakeWebViewClient_11(this, Invocation.method(#pigeon_copy, [])),
+            returnValue: _FakeWebViewClient_12(this, Invocation.method(#pigeon_copy, [])),
           )
           as _i2.WebViewClient);
 }
@@ -1024,7 +1042,7 @@ class MockWebViewProxy extends _i1.Mock implements _i7.WebViewProxy {
   _i2.WebView createWebView() =>
       (super.noSuchMethod(
             Invocation.method(#createWebView, []),
-            returnValue: _FakeWebView_4(this, Invocation.method(#createWebView, [])),
+            returnValue: _FakeWebView_5(this, Invocation.method(#createWebView, [])),
           )
           as _i2.WebView);
 
@@ -1054,7 +1072,7 @@ class MockWebViewProxy extends _i1.Mock implements _i7.WebViewProxy {
               #onReceivedSslError: onReceivedSslError,
               #urlLoading: urlLoading,
             }),
-            returnValue: _FakeWebViewClient_11(
+            returnValue: _FakeWebViewClient_12(
               this,
               Invocation.method(#createWebViewClient, [], {
                 #onPageStarted: onPageStarted,
diff --git a/packages/webview_flutter/webview_flutter_platform_interface/CHANGELOG.md b/packages/webview_flutter/webview_flutter_platform_interface/CHANGELOG.md
index 8325f522befa..7da6bcf9be79 100644
--- a/packages/webview_flutter/webview_flutter_platform_interface/CHANGELOG.md
+++ b/packages/webview_flutter/webview_flutter_platform_interface/CHANGELOG.md
@@ -1,5 +1,7 @@
-## NEXT
+## 2.16.0
 
+* Adds `addDocumentStartJavaScript` to `PlatformWebViewController` and the
+  `PlatformDocumentStartJavaScriptRegistration` class that it returns.
 * Updates minimum supported SDK version to Flutter 3.38/Dart 3.10.
 
 ## 2.15.1
diff --git a/packages/webview_flutter/webview_flutter_platform_interface/lib/src/platform_webview_controller.dart b/packages/webview_flutter/webview_flutter_platform_interface/lib/src/platform_webview_controller.dart
index a2ebeb2e4e47..3f9c8c27f328 100644
--- a/packages/webview_flutter/webview_flutter_platform_interface/lib/src/platform_webview_controller.dart
+++ b/packages/webview_flutter/webview_flutter_platform_interface/lib/src/platform_webview_controller.dart
@@ -168,6 +168,29 @@ abstract class PlatformWebViewController extends PlatformInterface {
     throw UnimplementedError('runJavaScript is not implemented on the current platform');
   }
 
+  /// Adds JavaScript that runs at the start of future document loads.
+  ///
+  /// This method should be called before loading a page if the script needs to
+  /// run for that page. It does not run JavaScript in the currently loaded
+  /// document. Implementations must run scripts in the order in which they were
+  /// added.
+  ///
+  /// The script runs in every frame of a loaded document, regardless of its
+  /// origin, including cross-origin `<iframe>`s.
+  ///
+  /// The returned [PlatformDocumentStartJavaScriptRegistration] can be used to stop
+  /// injecting the JavaScript into future document loads.
+  ///
+  /// Implementations that cannot support this feature should throw an
+  /// [UnsupportedError].
+  Future<PlatformDocumentStartJavaScriptRegistration> addDocumentStartJavaScript(
+    String javaScript,
+  ) {
+    throw UnimplementedError(
+      'addDocumentStartJavaScript is not implemented on the current platform',
+    );
+  }
+
   /// Runs the given JavaScript in the context of the current page, and returns the result.
   ///
   /// The Future completes with an error if a JavaScript error occurred, or if the
@@ -329,6 +352,18 @@ abstract class PlatformWebViewController extends PlatformInterface {
   }
 }
 
+/// A registration for JavaScript injected at the start of future document loads.
+///
+/// Returned by [PlatformWebViewController.addDocumentStartJavaScript].
+abstract class PlatformDocumentStartJavaScriptRegistration {
+  /// Creates a [PlatformDocumentStartJavaScriptRegistration].
+  @protected
+  const PlatformDocumentStartJavaScriptRegistration();
+
+  /// Deregisters this registration, stopping JavaScript injection into future document loads.
+  Future<void> remove();
+}
+
 /// Describes the parameters necessary for registering a JavaScript channel.
 @immutable
 class JavaScriptChannelParams {
diff --git a/packages/webview_flutter/webview_flutter_platform_interface/pubspec.yaml b/packages/webview_flutter/webview_flutter_platform_interface/pubspec.yaml
index 2d79e0281639..3aaac01d3045 100644
--- a/packages/webview_flutter/webview_flutter_platform_interface/pubspec.yaml
+++ b/packages/webview_flutter/webview_flutter_platform_interface/pubspec.yaml
@@ -4,7 +4,7 @@ repository: https://github.com/flutter/packages/tree/main/packages/webview_flutt
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+webview_flutter%22
 # NOTE: We strongly prefer non-breaking changes, even at the expense of a
 # less-clean API. See https://flutter.dev/go/platform-interface-breaking-changes
-version: 2.15.1
+version: 2.16.0
 
 environment:
   sdk: ^3.10.0
diff --git a/packages/webview_flutter/webview_flutter_platform_interface/test/platform_document_start_java_script_test.dart b/packages/webview_flutter/webview_flutter_platform_interface/test/platform_document_start_java_script_test.dart
new file mode 100644
index 000000000000..ab41ddba64dd
--- /dev/null
+++ b/packages/webview_flutter/webview_flutter_platform_interface/test/platform_document_start_java_script_test.dart
@@ -0,0 +1,26 @@
+// Copyright 2013 The Flutter Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:webview_flutter_platform_interface/webview_flutter_platform_interface.dart';
+
+void main() {
+  test('remove is forwarded to the implementation', () async {
+    final documentStartJavaScript = ExtendsPlatformDocumentStartJavaScriptRegistration();
+
+    await documentStartJavaScript.remove();
+
+    expect(documentStartJavaScript.removeCallCount, 1);
+  });
+}
+
+class ExtendsPlatformDocumentStartJavaScriptRegistration
+    extends PlatformDocumentStartJavaScriptRegistration {
+  int removeCallCount = 0;
+
+  @override
+  Future<void> remove() async {
+    removeCallCount += 1;
+  }
+}
diff --git a/packages/webview_flutter/webview_flutter_platform_interface/test/platform_webview_controller_test.dart b/packages/webview_flutter/webview_flutter_platform_interface/test/platform_webview_controller_test.dart
index 50db95e3264c..1855ab577f81 100644
--- a/packages/webview_flutter/webview_flutter_platform_interface/test/platform_webview_controller_test.dart
+++ b/packages/webview_flutter/webview_flutter_platform_interface/test/platform_webview_controller_test.dart
@@ -180,6 +180,14 @@ void main() {
     expect(() => controller.runJavaScript('javaScript'), throwsUnimplementedError);
   });
 
+  test('Default implementation of addDocumentStartJavaScript should throw unimplemented error', () {
+    final PlatformWebViewController controller = ExtendsPlatformWebViewController(
+      const PlatformWebViewControllerCreationParams(),
+    );
+
+    expect(() => controller.addDocumentStartJavaScript('javaScript'), throwsUnimplementedError);
+  });
+
   test(
     'Default implementation of runJavaScriptReturningResult should throw unimplemented error',
     () {
diff --git a/packages/webview_flutter/webview_flutter_web/CHANGELOG.md b/packages/webview_flutter/webview_flutter_web/CHANGELOG.md
index 0779794d3937..e6e1790dc931 100644
--- a/packages/webview_flutter/webview_flutter_web/CHANGELOG.md
+++ b/packages/webview_flutter/webview_flutter_web/CHANGELOG.md
@@ -1,5 +1,7 @@
-## NEXT
+## 0.2.4
 
+* Adds `addDocumentStartJavaScript`, which throws an `UnsupportedError` since
+  document-start JavaScript injection is not supported on the web.
 * Updates minimum supported SDK version to Flutter 3.38/Dart 3.10.
 
 ## 0.2.3+4
diff --git a/packages/webview_flutter/webview_flutter_web/lib/src/web_webview_controller.dart b/packages/webview_flutter/webview_flutter_web/lib/src/web_webview_controller.dart
index 2012c8c2dd91..b2bbe2389992 100644
--- a/packages/webview_flutter/webview_flutter_web/lib/src/web_webview_controller.dart
+++ b/packages/webview_flutter/webview_flutter_web/lib/src/web_webview_controller.dart
@@ -83,6 +83,17 @@ class WebWebViewController extends PlatformWebViewController {
     }
   }
 
+  /// Always throws an [UnsupportedError].
+  ///
+  /// Content is rendered in an `<iframe>`, which provides no way to inject a
+  /// script into a document before it loads.
+  @override
+  Future<PlatformDocumentStartJavaScriptRegistration> addDocumentStartJavaScript(
+    String javaScript,
+  ) async {
+    throw UnsupportedError('Document-start JavaScript injection is not supported on web.');
+  }
+
   /// Performs an AJAX request defined by [params].
   Future<void> _updateIFrameFromXhr(LoadRequestParams params) async {
     final response =
diff --git a/packages/webview_flutter/webview_flutter_web/pubspec.yaml b/packages/webview_flutter/webview_flutter_web/pubspec.yaml
index d1e13da8162d..56da1957c966 100644
--- a/packages/webview_flutter/webview_flutter_web/pubspec.yaml
+++ b/packages/webview_flutter/webview_flutter_web/pubspec.yaml
@@ -2,7 +2,7 @@ name: webview_flutter_web
 description: A Flutter plugin that provides a WebView widget on web.
 repository: https://github.com/flutter/packages/tree/main/packages/webview_flutter/webview_flutter_web
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+webview%22
-version: 0.2.3+4
+version: 0.2.4
 
 environment:
   sdk: ^3.10.0
@@ -22,7 +22,7 @@ dependencies:
   flutter_web_plugins:
     sdk: flutter
   web: ">=0.5.1 <2.0.0"
-  webview_flutter_platform_interface: ^2.0.0
+  webview_flutter_platform_interface: ^2.16.0
 
 dev_dependencies:
   build_runner: ^2.1.5
diff --git a/packages/webview_flutter/webview_flutter_web/test/web_webview_controller_test.dart b/packages/webview_flutter/webview_flutter_web/test/web_webview_controller_test.dart
index 7958a1297248..8545b717e4fa 100644
--- a/packages/webview_flutter/webview_flutter_web/test/web_webview_controller_test.dart
+++ b/packages/webview_flutter/webview_flutter_web/test/web_webview_controller_test.dart
@@ -212,5 +212,14 @@ void main() {
         );
       });
     });
+
+    test('addDocumentStartJavaScript is unsupported', () async {
+      final controller = WebWebViewController(WebWebViewControllerCreationParams());
+
+      await expectLater(
+        () async => controller.addDocumentStartJavaScript('window.test = true;'),
+        throwsA(isA<UnsupportedError>()),
+      );
+    });
   });
 }
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md b/packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md
index f5a9fd6ef336..aea328d05b3a 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md
+++ b/packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 3.27.0
+
+* Adds support for `addDocumentStartJavaScript`.
+
 ## 3.26.0
 
 * Adds new method for accessing a native `WKWebView` from a `FlutterPluginRegistrar`.
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart b/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
index 7cdf93cf8ba0..e1d06c7ae474 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart
@@ -33,6 +33,15 @@ Future<void> main() async {
         request.response.writeln('How are you today?');
       } else if (request.uri.path == '/headers') {
         request.response.writeln('${request.headers}');
+      } else if (request.uri.path == '/document-start.html') {
+        request.response.headers.contentType = ContentType.html;
+        // The inline script records the state of the window at parse time, so
+        // that a test can verify that injected scripts ran before it.
+        request.response.writeln(
+          '<!DOCTYPE html><html><head> '
+          '<script>window.recordedAtParseTime = String(window.injectedAtDocumentStart);</script> '
+          '</head><body>Document start test.</body></html>',
+        );
       } else if (request.uri.path == '/favicon.ico') {
         request.response.statusCode = HttpStatus.notFound;
       } else if (request.uri.path == '/http-basic-authentication') {
@@ -54,6 +63,7 @@ Future<void> main() async {
   final secondaryUrl = '$prefixUrl/secondary.txt';
   final headersUrl = '$prefixUrl/headers';
   final basicAuthUrl = '$prefixUrl/http-basic-authentication';
+  final documentStartUrl = '$prefixUrl/document-start.html';
 
   setUp(() {
     PigeonOverrides.pigeon_reset();
@@ -193,6 +203,44 @@ Future<void> main() async {
     await expectLater(controller.runJavaScriptReturningResult('1 + 1'), completion(2));
   });
 
+  testWidgets('addDocumentStartJavaScript', (WidgetTester tester) async {
+    final pageFinished = Completer<void>();
+    final messageReceived = Completer<String>();
+
+    final controller = PlatformWebViewController(const PlatformWebViewControllerCreationParams());
+    unawaited(controller.setJavaScriptMode(JavaScriptMode.unrestricted));
+    final delegate = PlatformNavigationDelegate(const PlatformNavigationDelegateCreationParams());
+    unawaited(delegate.setOnPageFinished((_) => pageFinished.complete()));
+    unawaited(controller.setPlatformNavigationDelegate(delegate));
+    await controller.addJavaScriptChannel(
+      JavaScriptChannelParams(
+        name: 'Echo',
+        onMessageReceived: (JavaScriptMessage message) => messageReceived.complete(message.message),
+      ),
+    );
+
+    await controller.addDocumentStartJavaScript('window.injectedAtDocumentStart = "injected";');
+    await controller.loadRequest(LoadRequestParams(uri: Uri.parse(documentStartUrl)));
+
+    await tester.pumpWidget(
+      Builder(
+        builder: (BuildContext context) {
+          return PlatformWebViewWidget(
+            PlatformWebViewWidgetCreationParams(controller: controller),
+          ).build(context);
+        },
+      ),
+    );
+
+    await pageFinished.future;
+
+    // The page records this value while it is being parsed, so a match proves
+    // that the script ran before the document's own scripts.
+    await controller.runJavaScript('Echo.postMessage(window.recordedAtParseTime);');
+
+    await expectLater(messageReceived.future, completion('injected'));
+  });
+
   testWidgets('loadRequest with headers', (WidgetTester tester) async {
     final headers = <String, String>{'test_header': 'flutter_test_header'};
 
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
index ffff87a1f43f..4b1a88437d87 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/lib/src/webkit_webview_controller.dart
@@ -317,6 +317,10 @@ class WebKitWebViewController extends PlatformWebViewController {
   final Map<String, WebKitJavaScriptChannelParams> _javaScriptChannelParams =
       <String, WebKitJavaScriptChannelParams>{};
 
+  /// Active document-start JavaScript registrations, in insertion order.
+  final List<WebKitDocumentStartJavaScriptRegistration> _documentStartJavaScriptRegistrations =
+      <WebKitDocumentStartJavaScriptRegistration>[];
+
   bool _zoomEnabled = true;
   WebKitNavigationDelegate? _currentNavigationDelegate;
 
@@ -447,6 +451,31 @@ class WebKitWebViewController extends PlatformWebViewController {
     ]);
   }
 
+  /// Adds JavaScript that runs at the start of future document loads.
+  ///
+  /// The script is added as a `WKUserScript` that is injected into all frames
+  /// at [UserScriptInjectionTime.atDocumentStart].
+  @override
+  Future<PlatformDocumentStartJavaScriptRegistration> addDocumentStartJavaScript(
+    String javaScript,
+  ) async {
+    final registration = WebKitDocumentStartJavaScriptRegistration._(this, javaScript);
+    await _addDocumentStartJavaScript(javaScript);
+    _documentStartJavaScriptRegistrations.add(registration);
+    return registration;
+  }
+
+  Future<void> _removeDocumentStartJavaScriptRegistration(
+    WebKitDocumentStartJavaScriptRegistration registration,
+  ) async {
+    if (!_documentStartJavaScriptRegistrations.remove(registration)) {
+      return;
+    }
+    // WKWebView does not support removing a single user script, so all user
+    // scripts are removed and the remaining ones are re-added.
+    await _resetUserScripts();
+  }
+
   @override
   Future<void> removeJavaScriptChannel(String javaScriptChannelName) async {
     assert(javaScriptChannelName.isNotEmpty);
@@ -795,7 +824,9 @@ class WebKitWebViewController extends PlatformWebViewController {
   Future<void> _resetUserScripts({String? removedJavaScriptChannel}) async {
     final WKUserContentController controller = await _webView.configuration
         .getUserContentController();
-    unawaited(controller.removeAllUserScripts());
+    // This is awaited so that it cannot remove the scripts that are re-added
+    // below.
+    await controller.removeAllUserScripts();
     // TODO(bparrishMines): This can be replaced with
     // `removeAllScriptMessageHandlers` once Dart supports runtime version
     // checking. (e.g. The equivalent to @availability in Objective-C.)
@@ -807,8 +838,7 @@ class WebKitWebViewController extends PlatformWebViewController {
     _javaScriptChannelParams.clear();
 
     await Future.wait(<Future<void>>[
-      for (final JavaScriptChannelParams params in remainingChannelParams.values)
-        addJavaScriptChannel(params),
+      _restoreJavaScriptChannelsAndDocumentStartScripts(remainingChannelParams.values),
       // Zoom is disabled with a WKUserScript, so this adds it back if it was
       // removed above.
       if (!_zoomEnabled) _disableZoom(),
@@ -818,6 +848,40 @@ class WebKitWebViewController extends PlatformWebViewController {
     ]);
   }
 
+  // JavaScript channels are restored before the document start scripts, since a
+  // document start script could reference a channel.
+  Future<void> _restoreJavaScriptChannelsAndDocumentStartScripts(
+    Iterable<WebKitJavaScriptChannelParams> channelParams,
+  ) async {
+    await Future.wait(<Future<void>>[
+      for (final WebKitJavaScriptChannelParams params in channelParams)
+        addJavaScriptChannel(params),
+    ]);
+    await _addAllDocumentStartJavaScriptRegistrations();
+  }
+
+  // These are added sequentially, since user scripts are run in the order they
+  // were added.
+  Future<void> _addAllDocumentStartJavaScriptRegistrations() async {
+    final registrations = List<WebKitDocumentStartJavaScriptRegistration>.of(
+      _documentStartJavaScriptRegistrations,
+    );
+    for (final registration in registrations) {
+      await _addDocumentStartJavaScript(registration._javaScript);
+    }
+  }
+
+  Future<void> _addDocumentStartJavaScript(String javaScript) async {
+    final userScript = WKUserScript(
+      source: javaScript,
+      injectionTime: UserScriptInjectionTime.atDocumentStart,
+      isForMainFrameOnly: false,
+    );
+    final WKUserContentController controller = await _webView.configuration
+        .getUserContentController();
+    await controller.addUserScript(userScript);
+  }
+
   Future<void> _disableZoom() async {
     final userScript = WKUserScript(
       source:
@@ -910,6 +974,23 @@ window.addEventListener("error", function(e) {
   }
 }
 
+/// An implementation of [PlatformDocumentStartJavaScriptRegistration] with the WebKit api.
+///
+/// See [WebKitWebViewController.addDocumentStartJavaScript].
+class WebKitDocumentStartJavaScriptRegistration
+    extends PlatformDocumentStartJavaScriptRegistration {
+  WebKitDocumentStartJavaScriptRegistration._(this._controller, this._javaScript);
+
+  final WebKitWebViewController _controller;
+
+  final String _javaScript;
+
+  @override
+  Future<void> remove() {
+    return _controller._removeDocumentStartJavaScriptRegistration(this);
+  }
+}
+
 /// An implementation of [JavaScriptChannelParams] with the WebKit api.
 ///
 /// See [WebKitWebViewController.addJavaScriptChannel].
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/pubspec.yaml b/packages/webview_flutter/webview_flutter_wkwebview/pubspec.yaml
index 5a1c07a9c271..733c727b7a45 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/pubspec.yaml
+++ b/packages/webview_flutter/webview_flutter_wkwebview/pubspec.yaml
@@ -2,7 +2,7 @@ name: webview_flutter_wkwebview
 description: A Flutter plugin that provides a WebView widget based on Apple's WKWebView control.
 repository: https://github.com/flutter/packages/tree/main/packages/webview_flutter/webview_flutter_wkwebview
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+webview%22
-version: 3.26.0
+version: 3.27.0
 
 environment:
   sdk: ^3.12.0
@@ -26,7 +26,7 @@ dependencies:
     sdk: flutter
   meta: ^1.10.0
   path: ^1.8.0
-  webview_flutter_platform_interface: ^2.15.1
+  webview_flutter_platform_interface: ^2.16.0
 
 dev_dependencies:
   build_runner: ^2.1.5
diff --git a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
index 757704666dfb..f5632f5336c6 100644
--- a/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
+++ b/packages/webview_flutter/webview_flutter_wkwebview/test/webkit_webview_controller_test.dart
@@ -889,6 +889,131 @@ void main() {
       expect(userScript.injectionTime, UserScriptInjectionTime.atDocumentStart);
     });
 
+    group('addDocumentStartJavaScript', () {
+      List<String> addedScriptSources(MockWKUserContentController userContentController) {
+        return verify(
+          userContentController.addUserScript(captureAny),
+        ).captured.cast<WKUserScript>().map((WKUserScript script) => script.source).toList();
+      }
+
+      test('adds a script for all frames at document start', () async {
+        final mockUserContentController = MockWKUserContentController();
+        final WebKitWebViewController controller = createControllerWithMocks(
+          mockUserContentController: mockUserContentController,
+        );
+
+        await controller.addDocumentStartJavaScript('window.test = true;');
+
+        final userScript =
+            verify(mockUserContentController.addUserScript(captureAny)).captured.single
+                as WKUserScript;
+        expect(userScript.source, 'window.test = true;');
+        expect(userScript.injectionTime, UserScriptInjectionTime.atDocumentStart);
+        expect(userScript.isForMainFrameOnly, isFalse);
+      });
+
+      test('allows the same JavaScript twice', () async {
+        final mockUserContentController = MockWKUserContentController();
+        final WebKitWebViewController controller = createControllerWithMocks(
+          mockUserContentController: mockUserContentController,
+        );
+
+        final PlatformDocumentStartJavaScriptRegistration first = await controller
+            .addDocumentStartJavaScript('window.test = true;');
+        final PlatformDocumentStartJavaScriptRegistration second = await controller
+            .addDocumentStartJavaScript('window.test = true;');
+
+        expect(first, isNot(same(second)));
+        verify(mockUserContentController.addUserScript(any)).called(2);
+      });
+
+      test('removing a script re-adds only the remaining scripts', () async {
+        final mockUserContentController = MockWKUserContentController();
+        final WebKitWebViewController controller = createControllerWithMocks(
+          mockUserContentController: mockUserContentController,
+        );
+
+        final PlatformDocumentStartJavaScriptRegistration first = await controller
+            .addDocumentStartJavaScript('window.first = true;');
+        await controller.addDocumentStartJavaScript('window.second = true;');
+        reset(mockUserContentController);
+
+        await first.remove();
+
+        // WKWebView can only remove all user scripts, so the remaining script
+        // is re-added.
+        verify(mockUserContentController.removeAllUserScripts());
+        expect(addedScriptSources(mockUserContentController), <String>['window.second = true;']);
+      });
+
+      test('removing a script more than once is a no-op', () async {
+        final mockUserContentController = MockWKUserContentController();
+        final WebKitWebViewController controller = createControllerWithMocks(
+          mockUserContentController: mockUserContentController,
+        );
+
+        final PlatformDocumentStartJavaScriptRegistration registration = await controller
+            .addDocumentStartJavaScript('window.test = true;');
+        await registration.remove();
+        reset(mockUserContentController);
+
+        await registration.remove();
+
+        verifyNever(mockUserContentController.removeAllUserScripts());
+      });
+
+      test('is preserved when a JavaScript channel is removed', () async {
+        final mockUserContentController = MockWKUserContentController();
+        final WebKitWebViewController controller = createControllerWithMocks(
+          mockUserContentController: mockUserContentController,
+        );
+
+        await controller.addDocumentStartJavaScript('window.test = true;');
+        await controller.addJavaScriptChannel(
+          WebKitJavaScriptChannelParams(name: 'name', onMessageReceived: (JavaScriptMessage _) {}),
+        );
+        reset(mockUserContentController);
+
+        await controller.removeJavaScriptChannel('name');
+
+        verify(mockUserContentController.removeScriptMessageHandler('name'));
+        expect(addedScriptSources(mockUserContentController), <String>['window.test = true;']);
+      });
+
+      test('is re-added in order and after the JavaScript channels', () async {
+        final mockWebViewConfiguration = MockWKWebViewConfiguration();
+        final mockUserContentController = MockWKUserContentController();
+        final WebKitWebViewController controller = createControllerWithMocks(
+          mockWebViewConfiguration: mockWebViewConfiguration,
+          mockUserContentController: mockUserContentController,
+        );
+
+        await controller.addJavaScriptChannel(
+          WebKitJavaScriptChannelParams(name: 'name', onMessageReceived: (JavaScriptMessage _) {}),
+        );
+        await controller.addDocumentStartJavaScript('window.first = true;');
+        await controller.addDocumentStartJavaScript('window.second = true;');
+        await controller.enableZoom(false);
+        reset(mockUserContentController);
+
+        // Make each lookup faster than the previous one, so that the scripts
+        // would be added out of order if they were added in parallel.
+        var lookupCount = 0;
+        when(mockWebViewConfiguration.getUserContentController()).thenAnswer((_) async {
+          await Future<void>.delayed(Duration(milliseconds: 40 - 10 * lookupCount++));
+          return mockUserContentController;
+        });
+
+        await controller.enableZoom(true);
+
+        expect(addedScriptSources(mockUserContentController), <String>[
+          'window.name = webkit.messageHandlers.name;',
+          'window.first = true;',
+          'window.second = true;',
+        ]);
+      });
+    });
+
     test('addJavaScriptChannel requires channel with a unique name', () async {
       PigeonOverrides.wKScriptMessageHandler_new =
           ({