Configuration

Markdown Viewer Configuration and Data Boundaries

This page documents the runtime, storage, dependency, Docker, Cloudflare, and desktop configuration used by Markdown Viewer, including the boundaries between client-side Markdown editing and optional network features.

Browser and Desktop Storage

Key	Location	Purpose
markdownViewerTabs	localStorage, mirrored to Neutralino storage in desktop	Normal saved tabs, including local review threads. Temporary share/live tabs are excluded.
markdownViewerActiveTab	localStorage, mirrored in desktop	Active tab id.
markdownViewerUntitledCounter	localStorage, mirrored in desktop	Next Untitled document number.
markdownViewerGlobalState	localStorage, mirrored in desktop	Theme, direction, view mode, scroll sync, and other global UI preferences.
app-lang	localStorage	Selected UI language.
find-replace-docked	localStorage	Find and Replace panel dock preference.
markdownViewerPrivateMode	localStorage	Whether document-state persistence is disabled. This preference remains while document-state keys are cleared.

The desktop app starts by copying known Neutralino storage values back into localStorage, then writes through saveStorageItem() to keep both layers aligned.

Temporary shared content is intentionally not persisted:

• Share Snapshot tabs have kind: "share-snapshot".
• Live Share participant/host tabs are stripped or restored when leaving the session.

Private mode clears the normal document-state keys (markdownViewerTabs, markdownViewerActiveTab, markdownViewerUntitledCounter, and markdownViewerGlobalState) when enabled and prevents them from being written until the mode is turned off. Use Clear local data in the About dialog to clear the same local state without enabling private mode.

Client Libraries

The web build loads core libraries from CDN with Subresource Integrity where checked into index.html. Larger feature libraries are lazy-loaded from script.js only when needed.

Library	Source	Used For	Load Behavior
Bootstrap	CDN or prepared desktop copy	UI components	Initial page load
Bootstrap Icons	CDN or prepared desktop copy	Icons	Initial page load
github-markdown-css	CDN or prepared desktop copy	Preview styling	Initial page load
Marked	CDN or prepared desktop copy	Markdown parsing	Initial page load and worker
Highlight.js	CDN or prepared desktop copy	Code highlighting	Initial page load and worker
DOMPurify	CDN or prepared desktop copy	HTML sanitization	Initial page load
FileSaver.js	CDN or prepared desktop copy	Browser downloads	Initial page load
js-yaml	CDN or prepared desktop copy	Frontmatter parsing	Initial page load
MathJax	CDN or prepared desktop copy	LaTeX math	Lazy
Mermaid	CDN or prepared desktop copy	Mermaid diagrams	Lazy
jsPDF	CDN or prepared desktop copy	Legacy raster PDF	Lazy
html2canvas	CDN or prepared desktop copy	PDF/PNG capture	Lazy
Pako	CDN or prepared desktop copy	Share compression, diagram encoding	Lazy
JoyPixels / emoji-toolkit	CDN or prepared desktop copy	Emoji shortcodes	Lazy
ABCJS	CDN or prepared desktop copy	ABC notation and playback	Lazy
Leaflet	CDN or prepared desktop copy	GeoJSON/TopoJSON maps	Lazy
TopoJSON	CDN or prepared desktop copy	TopoJSON conversion	Lazy
Three.js	CDN or prepared desktop copy	STL 3D rendering	Lazy
STLLoader / OrbitControls	CDN or prepared desktop copy	STL loading and controls	Lazy
D3	CDN or prepared desktop copy	Markmap	Lazy
Markmap	CDN or prepared desktop copy	Markmap diagrams	Lazy
Yjs	CDN or prepared desktop copy	Live Share document sync	Lazy

When running inside Neutralino, dynamic library URLs are rewritten to local /libs/... files prepared by desktop-app/prepare.js.

Rendering Thresholds and Limits

Setting	Value
Large document threshold	15,000 characters
Huge document threshold	100,000 characters
Worker render threshold	50,000 characters
Worker timeout	12 seconds
Small render debounce	100 ms
Large render debounce	160 ms
Huge render debounce	240 ms
Minimum split pane width	20%
Line-height cache size	5,000 entries
GitHub importer shown files	30
Share URL warning ceiling	32,000 characters
Legacy share URL ceiling	4,096 characters
Server share threshold	3,000 bytes
Stored Share Snapshot max content	500,000 characters
Stored Share Snapshot TTL	90 days
Live Share max participants	64
Live Share max message	1 MB
STL source limit	2 MiB
STL geometry limit	300,000 vertices

Sanitization

The main preview path calls DOMPurify with additional tags and attributes needed by renderers:

• Additional tags include mjx-container and input.
• Additional attributes include id, class, style, align, type, checked, disabled, data-original-code, role, aria-labelledby, and aria-describedby.
• Allowed URI schemes include HTTP(S), mailto:, tel:, blob:, relative URLs, and safe non-script values.

Export paths use similar expanded sanitizer settings for SVG/math capture. Scripts and unsafe event handlers are still removed.

Standalone HTML export also includes a restrictive CSP and SRI metadata for its external CSS and renderer scripts where applicable.

Service Worker and PWA

sw.js uses a versioned cache name so stale caches can be retired safely.

Critical assets:

• /
• /index.html
• /styles.css
• /script.js
• /preview-worker.js
• /manifest.json
• /assets/icon.jpg

Local shell assets use network-first behavior with cache fallback for update-sensitive paths. CDN assets from cdnjs and jsDelivr use cache-first behavior after first successful fetch. The service worker removes old markdown-viewer-cache-* caches on activation.

Service workers require HTTPS or localhost. They do not work from file://.

Cloudflare Configuration

wrangler.toml configures the Pages project:

name = "markdown-viewer"
pages_build_output_dir = "."
compatibility_date = "2025-04-30"

[[kv_namespaces]]
binding = "SHARE_KV"
id = "c820d2705f5742858a27b91b88f544bd"

[[durable_objects.bindings]]
name = "LIVE_ROOMS"
class_name = "LiveRoom"
script_name = "markdown-viewer-live-room"

SHARE_KV stores large Share Snapshot records for 90 days. LIVE_ROOMS routes Live Share WebSocket rooms to Durable Objects. Share Snapshot and Live Share are separate systems.

wrangler.live-room.toml deploys workers/live-room-worker.js with the LiveRoom Durable Object migration.

Share API

functions/api/share/[[id]].js supports:

• OPTIONS for CORS preflight.
• POST /api/share to create a stored snapshot.
• GET /api/share/<id> to load a stored snapshot.
• DELETE /api/share/<id> to delete a stored snapshot when the creator supplies its deletion token.

Responses set Cache-Control: no-store and vary CORS by request origin. The allowed origins are the production app, null, and localhost/127.0.0.1 development origins; unsupported origins receive 403. Stored records contain content, mode, title, creation time, size, and a hash of the creator deletion token. The token is returned only when the snapshot is created. Invalid ids, missing content, oversized content, invalid deletion tokens, missing KV binding, and unknown routes return JSON errors.

Live Room API

functions/live-room/[[room]].js supports WebSocket upgrades only. It validates the WebSocket Origin, room and secret length, requires LIVE_ROOMS, and forwards to a Durable Object chosen by roomName + ":" + secret. The Durable Object authenticates host, edit, and view capabilities, filters message types by role, and enforces the participant/message limits.

See Live Share Cloudflare for runtime flow and limits.

Docker and Nginx

The root Docker build serves static files with Nginx on port 80. The repository includes docker-compose.yml exposing 8080:80.

Security headers configured in Docker/Nginx documentation include:

• Strict-Transport-Security (Cloudflare Pages)
• Content-Security-Policy
• X-Frame-Options: DENY (Cloudflare Pages; the Docker image has its own Nginx policy)
• X-Content-Type-Options: nosniff
• Referrer-Policy: strict-origin-when-cross-origin
• Permissions-Policy
• Cross-Origin-Opener-Policy and Cross-Origin-Resource-Policy

Cloudflare Pages reads the root _headers and _redirects files. _redirects hides .env, _headers, and source-map paths behind 404 responses. Self-hosters should preserve equivalent policies and make sure preview-worker.js, sw.js, manifest.json, script.js, styles.css, assets/, workers/, and functions/ or their Cloudflare equivalents are deployed according to the features they intend to use.

Neutralino Desktop Configuration

Current desktop-app/neutralino.config.json highlights:

Setting	Value
applicationId	com.markdownviewer.desktop
documentRoot	/resources/
url	/
enableServer	true
enableNativeAPI	true
tokenSecurity	one-time
Default window	1280 x 720
Minimum window	400 x 200
Logging	disabled
Binary name	markdown-viewer

Native allowlist:

• app.exit
• os.showOpenDialog
• os.showSaveDialog
• os.showMessageBox
• os.open
• os.setTray
• filesystem.readFile
• filesystem.writeFile
• storage.setData
• storage.getData

os.execCommand is intentionally absent from the default allowlist. The desktop renderer therefore cannot execute local shell commands through the standard configuration.

The browser/chrome modes block filesystem and/or OS APIs more aggressively.

Desktop Build Scripts

desktop-app/package.json contains:

Script	Command Purpose
setup	Runs setup-binaries.js to install Neutralino binaries.
postsetup	Runs prepare.js.
predev	Runs setup before development.
dev	Runs npx -y @neutralinojs/neu@11.7.0 run.
prebuild	Runs setup before build.
build	Runs npx -y @neutralinojs/neu@11.7.0 build --release --clean and removes the release zip if present.

prepare.js copies root app files into desktop-app/resources, downloads and verifies libraries, rewrites dynamic library paths, strips web-only SEO metadata, and prepares local renderer/export resources for the desktop bundle.