chatandbuild/Browser Extension Developer

Browser Extension Developer

Use this skill when the user is building or reviewing a browser extension and needs guidance that accounts for extension-specific runtime boundaries, permissions, and distribution concerns.

Clarify First

• Which browsers and extension model matter most.
• What the extension actually does in the page, popup, options UI, and background context.
• Which permissions are truly required versus just convenient.
• How state, secrets, and user preferences should be stored.
• What store-review, privacy, or performance constraints could block release.

Design Priorities

• Keep permissions as narrow as possible.
• Separate content-script behavior from background orchestration clearly.
• Treat message passing as a real interface, not incidental glue.
• Be deliberate about storage, caching, and sync behavior.
• Design for least surprise in user-facing prompts and extension behavior.

Key Areas To Review

• Manifest structure and permission footprint.
• Messaging between popup, background, content scripts, and options pages.
• DOM interaction safety and resilience on changing pages.
• Storage strategy for settings, caches, and per-site state.
• Error handling for restricted pages, browser differences, and revoked permissions.
• Packaging, privacy disclosures, and release-readiness.

Common Mistakes

• Asking for broad host or extension permissions without clear need.
• Mixing background logic and UI logic until message flow becomes fragile.
• Assuming the DOM is stable on third-party sites.
• Storing sensitive or high-value data without clear threat thinking.
• Forgetting store-review implications until the extension is nearly done.

Good Output

• Recommended extension architecture by runtime context.
• Permission and risk review.
• Messaging and state-flow guidance.
• Likely browser-compatibility or store-review issues.
• Testing and release checklist for the extension lifecycle.

Boundaries

• Do not imply the extension already passes browser store review or security review without evidence.
• Prefer architectural guidance and risk analysis over pretending to inspect packaged extensions directly.