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web-extension

Design, build, and debug browser extensions for Chromium, Firefox, and Safari.

1|Updated May 12, 2026
Search Tags:#cross-browser#browser extension#manifest v3#content scripts#webextensions#extension messaging
One-click install
npx skills add https://github.com/Firzus/agent-skills --skill web-extension
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: web-extension
Source: https://github.com/Firzus/agent-skills/tree/main/skills/web/web-extension
Command: npx skills add https://github.com/Firzus/agent-skills --skill web-extension

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

This Skill helps you design, implement, debug, and release browser extensions without getting tripped up by browser-specific APIs, manifest differences, permissions, or lifecycle quirks.

Core Features & Use Cases

  • Cross-browser extension planning: Map capabilities across Chromium, Firefox, and Safari before writing code.
  • Architecture and messaging: Separate content scripts, background logic, extension pages, and page code with validated message boundaries.
  • Permissions and security: Keep host access narrow, validate sender and payloads, and avoid unsafe code patterns.
  • Testing and release readiness: Check install, reload, restart, upgrade, packaging, and store submission requirements for each target.
  • Use Case: A team migrating a Chrome extension to Firefox and Safari can use this Skill to identify incompatible APIs, adjust manifests, and prepare store-ready packages.

Quick Start

Ask for a cross-browser implementation plan for your extension idea, including the target browsers, required permissions, execution contexts, and any manifest or packaging changes needed.

Frequently Asked Questions about web-extension

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I build a browser extension that works across Chromium, Firefox, and Safari?▼

You can build cross-browser extensions using the WebExtensions model, which maps capabilities across target browsers, adjusts manifest differences, and validates browser-specific APIs for universal compatibility.

How do I migrate a Chrome extension to Firefox and Safari?▼

Migrating a Chrome extension to Firefox and Safari requires identifying incompatible APIs, adjusting the manifest for cross-browser compatibility, and preparing store-ready packages for each specific browser target.

What is Manifest V3 and how does it affect background service workers?▼

Manifest V3 replaces persistent background pages with service workers, requiring restart-safe background behavior and adjusted extension messaging to maintain functionality across browser lifecycle events.

How should I structure extension messaging between content scripts and background logic?▼

Structure extension messaging by separating content scripts, background logic, and extension pages with validated message boundaries, validating sender origins and payloads to avoid unsafe code patterns.

What permissions do I need for least-privilege access in web extensions?▼

Least-privilege access requires keeping host access narrow and avoiding unsafe code patterns, ensuring the extension only requests permissions essential for its specific functionality across target browsers.

How do I test and package a browser extension for store submission?▼

Testing and packaging for store submission requires checking install, reload, restart, and upgrade behaviors, validating browser-specific release requirements, and preparing store-ready packages for each target browser.

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