How to add Firefox DevTools MCP to Claude Desktop

Automate and inspect Firefox via WebDriver BiDi (Selenium) from any MCP client. Paste the config into ~/Library/Application Support/Claude/claude_desktop_config.json and restart Claude Desktop.

Last updated June 14, 2026 · 228★ · stdio · no auth · official

Claude Desktop config for Firefox DevTools MCP

claude mcp add firefox-devtools npx @mozilla/firefox-devtools-mcp@latest

{
  "mcpServers": {
    "firefox-devtools-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "@mozilla/firefox-devtools-mcp@latest",
        "--headless",
        "--viewport",
        "1280x720"
      ],
      "env": {
        "START_URL": "about:blank"
      }
    }
  }
}

Setup steps

1Open Claude Desktop → Settings → Developer → Edit Config (this opens ~/Library/Application Support/Claude/claude_desktop_config.json).
2Paste the Firefox DevTools MCP config below under the top-level "mcpServers" key.
3Fill in any placeholder secrets (API keys, paths) in the snippet.
4Save the file, then fully quit and reopen Claude Desktop.
5Open a chat and confirm Firefox DevTools MCP's tools appear under the 🔌 tools menu.

Before you start

Node.js >= 20.19.0
Firefox 100+ installed locally (auto-detected, or pass --firefox-path)
For Firefox for Android: adb on your PATH (geckodriver is managed automatically)

What Firefox DevTools MCP can do in Claude Desktop

list_pages

List the open pages (tabs) in the browser.

new_page

Open a new page (tab).

navigate_page

Navigate the selected page to a URL.

select_page

Select the active page to operate on.

close_page

Close a page (tab).

take_snapshot

Take an accessibility-tree snapshot of the page, producing UIDs for elements.

click_by_uid

Click an element identified by its snapshot UID.

hover_by_uid

Hover over an element identified by its snapshot UID.

Security

Browser MCP servers carry inherent risks. Use a dedicated Firefox profile (never your regular one) since the agent can access whatever the browser can reach, including cookies and saved sessions. Be cautious about which sites you visit, as pages can return content designed to manipulate the agent (prompt injection). Avoid enabling extra flags unless needed: `--enable-script` and `--enable-privileged-context` significantly expand what the agent can do. Do not leave Marionette enabled during normal browsing in connect-existing mode, as it changes browser fingerprint signals and can trigger bot detection. See SECURITY.md for a full breakdown.

Firefox DevTools MCP + Claude Desktop FAQ

Where is the Claude Desktop config file?

Claude Desktop reads MCP servers from ~/Library/Application Support/Claude/claude_desktop_config.json. Paste the Firefox DevTools MCP config there under the "mcpServers" key and restart the client.

Is Firefox DevTools MCP safe to use with Claude Desktop?

Can this run on a cloud MCP host like glama.ai?

No. The server requires a local Firefox browser installation and cannot run on cloud hosting services. Run it locally with `npx @mozilla/firefox-devtools-mcp@latest`, or use Docker with the provided Dockerfile.

How do I run arbitrary JavaScript in the page?

The evaluate_script tool is disabled by default. Enable it with the --enable-script flag (or ENABLE_SCRIPT=true). Privileged scripts and other privileged-context tools additionally require --enable-privileged-context and MOZ_REMOTE_ALLOW_SYSTEM_ACCESS=1.

Can I automate my real, logged-in Firefox session?

Yes, via connect-existing mode: start Firefox with `firefox --marionette`, then run the server with `--connect-existing --marionette-port 2828`. BiDi-dependent features (console and network events) are unavailable in this mode, but all other features work. Do not leave Marionette enabled during normal browsing, as it changes fingerprint signals and can trigger bot detection.

View repo Full Firefox DevTools MCP page