Chrome to Firefox Extension Converter

A Rust-based CLI tool and WebAssembly library that converts Chrome Manifest V3 extensions to Firefox-compatible format.

Live Demo: https://otsobear.github.io/chrome2moz/

Why This Tool?

Firefox natively supports chrome.* APIs, but some Chrome-only APIs don't exist in Firefox. This tool:

Detects 176 Chrome-only APIs (e.g., chrome.offscreen, chrome.declarativeContent, chrome.tabGroups)
Converts manifests (service workers → event pages, permission separation)
Provides runtime shims for Chrome-only APIs
Checks keyboard shortcuts for conflicts with Firefox built-ins

Read more: ARCHITECTURE.md covers Chrome API detection system, detection scope, and keyboard shortcuts in detail.

Features

Smart Detection: Identifies Chrome-only APIs that need conversion
Manifest Transformation: Handles MV3 manifest differences for Firefox
Keyboard Shortcut Checker: Detects conflicts with 60+ Firefox shortcuts
Multiple Formats: Supports .crx, .zip, or unpacked directories
Web Interface: Browser-based UI (no installation required)

Quick Start

Web UI (Recommended)

./build-wasm.sh
cd web && python3 -m http.server 8080
Open http://localhost:8080

Drag & drop your Chrome extension ZIP, analyze, and download the converted Firefox version.

CLI

# Install
git clone https://github.com/OtsoBear/chrome2moz.git
cd chrome2moz
cargo build --release
Analyze
./target/release/chrome2moz analyze -i ./chrome-extension
Convert
./target/release/chrome2moz convert -i ./chrome-extension -o ./output
List Chrome-only APIs
./target/release/chrome2moz chrome-only-apis

Options: --report (generate report), --yes (skip prompts), --preserve-chrome (keep both namespaces)

What Gets Converted

Chrome-Only APIs → Runtime shims provided for:

chrome.storage.session → In-memory polyfill
chrome.sidePanel → Firefox sidebarAction
chrome.offscreen → Web Workers/content scripts
chrome.declarativeContent → Content script patterns
chrome.tabGroups → No-op stub (Firefox doesn't support)
And more... (see ARCHITECTURE.md)

Manifest Changes:

background.service_worker → background.scripts (event page)
Add browserspecificsettings.gecko for Firefox ID
Separate permissions from host_permissions
Convert webaccessibleresources format
Handle importScripts() → Add to manifest

Firefox Compatibility Fixes:

Automatically disables browser.management.uninstallSelf() calls
Prevents extensions from self-destructing when detecting Firefox
See docs/FIREFOXSELFUNINSTALL_FIX.md for details

API Coverage

View Full API Status →

Testing in Firefox

Open about:debugging#/runtime/this-firefox
Click "Load Temporary Add-on"
Select the converted manifest.json or .xpi file

Check Browser Console (Ctrl+Shift+J) for any errors.

Important Notes

Firefox supports chrome. namespace natively - no need to rewrite to browser.
Static analysis has limits - runtime behavior differences need manual testing
~90% of conversions work automatically; remaining 10% may need manual adjustments
See ARCHITECTURE.md for what's detected vs. what requires testing