Unable to add `page_action` to Firefox MV3

[smashedr]

Describe the bug

Firefox MV3 still uses page_action but WXT strips this in every step and provides no way to include it.

• https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/page_action

I have tried both adding page_action to both the main manifest section and the manifestGenerated hook, but in all cases it gets stripped.

  hooks: {
    'build:manifestGenerated': (wxt, manifest) => {
      console.log('wxt.config.browser', wxt.config.browser)
      if (wxt.config.browser === 'firefox') {
        manifest.page_action = {
          default_popup: 'popup.html',
          default_icon: icons,
          show_matches: ['*://*/*'],
        }
      }
    },
  },

---

At a glance, in searching for an existing issue, I found what my be a related issue:

• Automatically strip MV2 keys from manifest when targetting MV3, and vise-versa. #517

Reproduction

I can't find any way to get the page_action to be included in the Firefox MV3 manifest.json.

If you need a project this has the page_action manifest keys: https://github.com/smashedr/wxt-extension

Steps to reproduce

wxt -b firefox --mv3
wxt build -b firefox --mv3

The page_action will be stripped int he manifest.json in both cases.

System Info

Binaries:
    Node: 24.11.0 - C:\Apps\node-v24.11.0-win-x64\node.EXE
    Yarn: 1.22.22 - C:\Apps\node-v24.11.0-win-x64\yarn.CMD
    npm: 11.11.1 - C:\Apps\node-v24.11.0-win-x64\npm.CMD
    pnpm: 10.28.0 - C:\Apps\node-v24.11.0-win-x64\pnpm.CMD

Used Package Manager

npm

Validations

• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[aklinker1]

Oh dang, I did not know that was a thing! Thanks for reporting, I've marked this issue as a good first issue for contributors, here's the part of the code that would need changed (along side tests, pnpm -f wxt test):

wxt/packages/wxt/src/core/utils/manifest.ts

Lines 267 to 301 in 41a687a

	if (popup) {
	const default_popup = getEntrypointBundlePath(
	popup,
	wxt.config.outDir,
	'.html',
	);
	const options: Browser.runtime.ManifestAction = {};
	if (popup.options.defaultIcon)
	options.default_icon = popup.options.defaultIcon;
	if (popup.options.defaultTitle)
	options.default_title = popup.options.defaultTitle;
	if (popup.options.browserStyle)
	// @ts-expect-error: Not typed by @wxt-dev/browser, but supported by Firefox
	options.browser_style = popup.options.browserStyle;
	if (popup.options.defaultArea)
	// @ts-expect-error: Not typed by @wxt-dev/browser, but supported by Firefox
	options.default_area = popup.options.defaultArea;
	if (popup.options.themeIcons)
	// @ts-expect-error: Not typed by @wxt-dev/browser, but supported by Firefox
	options.theme_icons = popup.options.themeIcons;
	if (manifest.manifest_version === 3) {
	manifest.action = {
	...manifest.action,
	...options,
	default_popup,
	};
	} else {
	const key = popup.options.mv2Key ?? 'browser_action';
	manifest[key] = {
	...manifest[key],
	...options,
	default_popup,
	};
	}
	}

wxt/packages/wxt/src/core/utils/manifest.ts

Lines 653 to 662 in 41a687a

	function convertActionToMv2(manifest: Browser.runtime.Manifest): void {
	if (
	manifest.action == null ||
	manifest.browser_action != null ||
	manifest.page_action != null
	)
	return;
	manifest.browser_action = manifest.action;
	}

wxt/packages/wxt/src/core/utils/manifest.ts

Lines 709 to 727 in 41a687a

	const mv2OnlyKeys = [
	'page_action',
	'browser_action',
	'automation',
	'content_capabilities',
	'converted_from_user_script',
	'current_locale',
	'differential_fingerprint',
	'event_rules',
	'file_browser_handlers',
	'file_system_provider_capabilities',
	'nacl_modules',
	'natively_connectable',
	'offline_enabled',
	'platforms',
	'replacement_web_app',
	'system_indicator',
	'user_scripts',
	];

All of it is in the manifest generation code.

[smashedr]

Was not sure how you wanted this added, but the manifest section was pretty straight forward.

I opened a PR to get the discussion started: #2200

[smashedr]

This is working as expected now.

Quick note on implementation, best to use the build hook to take advantage of already defined icons.

  // https://wxt.dev/guide/essentials/config/hooks
  hooks: {
    'build:manifestGenerated': (wxt, manifest) => {
      console.log('build:manifestGenerated:', wxt.config.browser)
      if (manifest.action) manifest.action.default_icon = manifest.icons
      if (manifest.sidebar_action) manifest.sidebar_action.default_icon = manifest.icons
      if (wxt.config.browser === 'firefox') {
        manifest.page_action = {
          default_popup: 'popup.html',
          default_icon: manifest.icons,
          show_matches: ['*://*/*'],
        }
      }
    },
  },