Browser Extension taste of a cross-browser extension developer

• Build on Manifest V3 and plan around service workers that can be stopped at any time. Confidence: 0.95
• Use a framework like WXT or Plasmo with TypeScript and Vite to handle builds, reloads and cross-browser manifests. Confidence: 0.80
• Request the fewest permissions possible, and prefer activeTab and optional_permissions over broad host access. Confidence: 0.95
• Never request the all_urls host permission unless the core feature truly needs every site. Confidence: 0.90
• Keep no important state in service worker globals and persist it with chrome.storage instead. Confidence: 0.95
• Use chrome.storage.session for temporary secrets and chrome.storage.local or sync for user settings, with a typed wrapper and defaults. Confidence: 0.85
• Use chrome.alarms for scheduled work instead of setInterval in the background. Confidence: 0.90
• Register all event listeners at the top level of the service worker so they survive restarts. Confidence: 0.90
• Keep content scripts small and inject them programmatically with chrome.scripting when possible. Confidence: 0.85
• Isolate injected UI in a Shadow DOM so page styles and extension styles cannot collide. Confidence: 0.90
• Treat every message from content scripts and web pages as untrusted and validate it with a schema. Confidence: 0.95
• Define message types in one shared module and use typed request and response helpers for runtime messaging. Confidence: 0.85
• Never inject remote code or use eval, and keep a strict Content Security Policy. Confidence: 0.95
• Use declarativeNetRequest for blocking or modifying requests instead of trying to intercept them in code. Confidence: 0.85
• Use the webextension-polyfill or a framework layer so the same code runs on Chrome, Firefox, Edge and Safari. Confidence: 0.80
• Collect as little user data as possible and explain clearly in the store listing what is stored and why. Confidence: 0.90
• Handle install and update events to migrate stored settings between versions. Confidence: 0.85
• Test popup and options pages as normal web UI, and run end-to-end tests with Playwright loading the unpacked extension. Confidence: 0.80
• Automate builds, version bumps and store uploads in CI, with one zip artifact per browser. Confidence: 0.80
• Keep the popup fast by loading heavy data lazily and showing cached state first. Confidence: 0.80
• Write a short permission justification for each permission before submitting to the store. Confidence: 0.85