Agent Skills: Community WXT Browser Extensions Best Practices

Community WXT Browser Extensions Best Practices

Comprehensive performance optimization guide for WXT browser extension development. Contains 49 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation. Updated for WXT v0.20+.

When to Apply

Reference these guidelines when:

• Writing new WXT browser extension code
• Implementing service worker background scripts
• Injecting content scripts into web pages
• Setting up messaging between extension contexts
• Configuring manifest permissions and resources

Rule Categories by Priority

| Priority | Category | Impact | Prefix | |----------|----------|--------|--------| | 1 | Service Worker Lifecycle | CRITICAL | svc- | | 2 | Content Script Injection | CRITICAL | inject- | | 3 | Messaging Architecture | HIGH | msg- | | 4 | Storage Patterns | HIGH | store- | | 5 | Bundle Optimization | MEDIUM-HIGH | bundle- | | 6 | Manifest Configuration | MEDIUM | manifest- | | 7 | UI Performance | MEDIUM | ui- | | 8 | TypeScript Patterns | LOW-MEDIUM | ts- |

Quick Reference

1. Service Worker Lifecycle (CRITICAL)

• svc-register-listeners-synchronously - Register listeners synchronously to prevent missed events
• svc-avoid-global-state - Use storage instead of in-memory state
• svc-keep-alive-patterns - Keep service worker alive for long operations
• svc-handle-install-update - Handle install and update lifecycle events
• svc-offscreen-documents - Use offscreen documents for DOM operations
• svc-declarative-net-request - Use declarative rules for network blocking

2. Content Script Injection (CRITICAL)

• inject-use-main-function - Place runtime code inside main() function
• inject-choose-correct-world - Select ISOLATED or MAIN world appropriately
• inject-run-at-timing - Configure appropriate runAt timing
• inject-use-ctx-invalidated - Handle context invalidation on update
• inject-dynamic-registration - Use runtime registration for conditional injection
• inject-all-frames - Configure allFrames for iframe handling
• inject-spa-navigation - Handle SPA navigation with wxt:locationchange

3. Messaging Architecture (HIGH)

• msg-type-safe-messaging - Use @webext-core/messaging for type-safe protocols
• msg-return-true-for-async - Return true for async message handlers (raw API)
• msg-use-tabs-sendmessage - Use tabs.sendMessage for content scripts
• msg-use-ports-for-streams - Use ports for streaming communication
• msg-handle-no-receiver - Handle missing message receivers
• msg-avoid-circular-messages - Prevent circular message loops

4. Storage Patterns (HIGH)

• store-use-define-item - Use storage.defineItem for type-safe access
• store-choose-storage-area - Select appropriate storage area
• store-batch-operations - Group related data into single defineItem
• store-watch-for-changes - Use watch() for reactive updates
• store-handle-quota-errors - Handle storage quota errors
• store-versioned-migrations - Use versioning for schema migrations

5. Bundle Optimization (MEDIUM-HIGH)

• bundle-split-entrypoints - Split code by entrypoint
• bundle-analyze-size - Analyze and monitor bundle size
• bundle-tree-shake-icons - Use direct imports for icon libraries
• bundle-externalize-wasm - Load WASM dynamically
• bundle-minify-content-scripts - Minimize content script size

6. Manifest Configuration (MEDIUM)

• manifest-minimal-permissions - Request minimal permissions
• manifest-use-optional-permissions - Use optional permissions progressively
• manifest-web-accessible-resources - Scope web accessible resources
• manifest-content-security-policy - Configure CSP correctly
• manifest-cross-browser-compatibility - Support multiple browsers

7. UI Performance (MEDIUM)

• ui-use-shadow-dom - Use Shadow DOM for injected UI
• ui-defer-rendering - Defer popup rendering until needed
• ui-cleanup-on-unmount - Clean up UI on unmount
• ui-sidepanel-persistence - Preserve sidepanel state
• ui-position-fixed-iframe - Use iframe for complex UI
• ui-avoid-layout-thrashing - Batch DOM reads and writes

8. TypeScript Patterns (LOW-MEDIUM)

• ts-use-imports-module - Use #imports virtual module and auto-imports
• ts-use-browser-not-chrome - Use browser namespace over chrome
• ts-type-entrypoint-options - Type entrypoint options explicitly
• ts-augment-browser-types - Augment types for missing APIs
• ts-strict-null-checks - Enable strict null checks
• ts-import-meta-env - Use import.meta for build info
• ts-avoid-any - Avoid any type in handlers
• ts-path-aliases - Use path aliases for imports

How to Use

Read individual reference files for detailed explanations and code examples:

• Section definitions - Category structure and impact levels
• Rule template - Template for adding new rules

Reference Files

| File | Description | |------|-------------| | references/_sections.md | Category definitions and ordering | | assets/templates/_template.md | Template for new rules | | metadata.json | Version and reference information |