How to install Firefox DevTools MCP in Gemini CLI

Control and debug Firefox: navigate, fill forms, inspect network and console, profile.

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We found Firefox DevTools MCP in the official MCP registry. Our automated check passed on Nov 1, 2026 (it confirms the server is published and reachable), but no one at CuratedMCP has reviewed its code, permissions or credentials handling. Check what it can access before you give it keys. Scan your machine free to see every MCP server you have installed.

Steps

1Install Node.js 18 or newer (for npx)
2Open ~/.gemini/settings.json (or .gemini/settings.json in your project)
3Add the entry below. If the file already has "mcpServers", add just the inner entry
4Restart Gemini CLI and run /mcp to confirm

Configuration

~/.gemini/settings.json

{
  "mcpServers": {
    "firefox-devtools": {
      "command": "npx",
      "args": [
        "-y",
        "@mozilla/firefox-devtools-mcp"
      ]
    }
  }
}

Environment variable	Required	What it is
FIREFOX_HEADLESS	No	Set to true to run Firefox without a visible window.
START_URL	No	URL to open when the server starts.

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