browser-extension-builder

Browser Extension Builder is a single-file guidance skill for designing and shipping Chrome, Firefox, and cross-browser extensions on Manifest V3. It casts Claude as a Browser Extension Architect who understands the platform's constraints — permissions, security, and store policies — and aims to help build extensions people install and use daily rather than throwaway toys. It solves the problem of scattered, quickly outdated extension knowledge by collecting architecture, APIs, storage, monetization, and publishing patterns in one place.

The skill walks through a canonical project structure (manifest, popup, content scripts, background service worker, options page, icons), a Manifest V3 template, and the popup-to-background-to-content-script communication model backed by chrome.storage. It provides example content scripts that read and modify page DOM and inject floating UI, storage patterns using chrome.storage.local and sync with documented limits and async wrappers, and monetization approaches (freemium, one-time, subscription, donations, affiliate) noting that Chrome discontinued built-in payments so checkout must run through an external site and backend. It also includes validation checks that flag anti-patterns such as using the deprecated Manifest V2 or requesting excessive permissions that risk store rejection.

It targets extension developers and indie makers planning, building, or publishing to the Chrome Web Store. The example manifest matches content scripts against all URLs, which is standard for general-purpose extensions but is a broad host-permission surface worth narrowing in production; the skill itself flags excessive permissions as a rejection risk. The source repo tags it 'risk: critical', but the content is ordinary developer education with example code and no malicious behavior.