Firefox DevTools MCP
Model Context Protocol server for automating Firefox via WebDriver BiDi (through Selenium WebDriver). Works with Claude Code, Claude Desktop, Cursor, Cline and other MCP clients.
Repository: https://github.com/freema/firefox-devtools-mcp
Note: This MCP server requires a local Firefox browser installation and cannot run on cloud hosting services like glama.ai. Use
npx firefox-devtools-mcp@latestto run locally, or use Docker with the provided Dockerfile.
Requirements
- Node.js ≥ 20.19.0
- Firefox 100+ installed (auto‑detected, or pass
--firefox-path)
Install and use with Claude Code (npx)
Recommended: use npx so you always run the latest published version from npm.
Option A — Claude Code CLI
claude mcp add firefox-devtools npx firefox-devtools-mcp@latest
Pass options either as args or env vars. Examples:
# Headless + viewport via args
claude mcp add firefox-devtools npx firefox-devtools-mcp@latest -- --headless --viewport 1280x720
# Or via environment variables
claude mcp add firefox-devtools npx firefox-devtools-mcp@latest \
--env START_URL=https://example.com \
--env FIREFOX_HEADLESS=true
Option B — Edit Claude Code settings JSON
Add to your Claude Code config file:
- macOS:
~/Library/Application Support/Claude/Code/mcp_settings.json - Linux:
~/.config/claude/code/mcp_settings.json - Windows:
%APPDATA%\Claude\Code\mcp_settings.json
{
"mcpServers": {
"firefox-devtools": {
"command": "npx",
"args": ["-y", "firefox-devtools-mcp@latest", "--headless", "--viewport", "1280x720"],
"env": {
"START_URL": "about:home"
}
}
}
}
Option C — Helper script (local dev build)
npm run setup
# Choose Claude Code; the script saves JSON to the right path
Try it with MCP Inspector
npx @modelcontextprotocol/inspector npx firefox-devtools-mcp@latest --start-url https://example.com --headless
Then call tools like:
list_pages,select_page,navigate_pagetake_snapshotthenclick_by_uid/fill_by_uidlist_network_requests(always‑on capture),get_network_requestscreenshot_page,list_console_messages
CLI options
You can pass flags or environment variables (names on the right):
--firefox-path— absolute path to Firefox binary--headless— run without UI (FIREFOX_HEADLESS=true)--viewport 1280x720— initial window size--profile-path— use a specific Firefox profile--firefox-arg— extra Firefox arguments (repeatable)--start-url— open this URL on start (START_URL)--accept-insecure-certs— ignore TLS errors (ACCEPT_INSECURE_CERTS=true)
Tool overview
- Pages: list/new/navigate/select/close
- Snapshot/UID: take/resolve/clear
- Input: click/hover/fill/drag/upload/form fill
- Network: list/get (ID‑first, filters, always‑on capture)
- Console: list/clear
- Screenshot: page/by uid
- Utilities: accept/dismiss dialog, history back/forward, set viewport
Local development
npm install
npm run build
# Run with Inspector against local build
npx @modelcontextprotocol/inspector node dist/index.js --headless --viewport 1280x720
# Or run in dev with hot reload
npm run inspector:dev
Troubleshooting
- Firefox not found: pass
--firefox-path "/Applications/Firefox.app/Contents/MacOS/firefox"(macOS) or the correct path on your OS. - First run is slow: Selenium sets up the BiDi session; subsequent runs are faster.
- Stale UIDs after navigation: take a fresh snapshot (
take_snapshot) before using UID tools.
Versioning
- Pre‑1.0 API: versions start at
0.x. Use@latestwith npx for the newest release.
CI and Release
- GitHub Actions for CI, Release, and npm publish are included. See docs/ci-and-release.md for details and required secrets.
Author
Created by Tomáš Grasl