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Firefox DevTools MCP

Mozilla-maintained MCP server for automating Firefox through WebDriver BiDi, with tools for page navigation, snapshots, UID-based input, screenshots, network requests, console messages, dialogs, history, viewport changes, optional JavaScript evaluation, privileged Firefox contexts, preferences, and WebExtension management.

by Mozilla·added 2026-06-06·
Claude CodeClaude Desktop
HarnessClaude CodeClaude Desktop
Review first — review before installing

Open the source and read safety notes before installing.

Safety notes

  • Browser pages can contain prompt-injection text in visible content, hidden HTML, ARIA labels, console output, network responses, or page metadata.
  • The server can navigate pages, click, hover, fill forms, drag, upload files, accept dialogs, dismiss dialogs, go through history, change viewport size, close tabs, and restart Firefox.
  • Enabling evaluate_script allows arbitrary JavaScript in page context; compromised instructions could read page data, modify the DOM, or interact with accessible browser APIs.
  • Enabling privileged context tools with the required Firefox system-access environment variable can expose privileged Firefox APIs and may extend beyond web-content sandbox boundaries.
  • Connect-existing mode can attach to a real browsing session with cookies, logins, active tabs, history, and saved state, so avoid it unless the profile is dedicated to automation.
  • Accepting insecure certificates weakens TLS validation and can hide man-in-the-middle or misconfiguration signals.

Privacy notes

  • Page content, DOM snapshots, accessibility labels, console messages, network requests, headers, screenshots, uploaded file paths, extension names, Firefox prefs, and browser logs can be sent to the MCP client and model.
  • A regular Firefox profile can expose cookies, saved sessions, browsing history, account data, extensions, and private tabs to browser automation.
  • Screenshot save paths, uploaded files, downloaded artifacts, and model transcripts can reveal local project names, test data, credentials shown on pages, or customer information.
  • Use a separate profile, minimize enabled capabilities, avoid sensitive sites, and review provider/browser data handling before automating logged-in sessions.

Prerequisites

  • Node.js 20.19.0 or newer.
  • Local Firefox 100 or newer, or an explicit Firefox binary path passed through the documented CLI option.
  • A dedicated Firefox automation profile with no personal cookies, saved passwords, or regular browsing sessions.
  • Optional adb and Firefox for Android setup when using Android automation mode.
  • Explicit approval before enabling JavaScript evaluation, privileged Firefox contexts, insecure certificates, extension management, or connect-existing mode.

Schema details

Install type
cli
Troubleshooting
No
Source repository stats
Scope
Source repo
Collection metadata
Estimated setup
10 minutes
Difficulty
intermediate
Tool listing metadata
Full copyable content
{
  "mcpServers": {
    "firefox-devtools": {
      "command": "npx",
      "args": ["-y", "firefox-devtools-mcp@latest"]
    }
  }
}

About this resource

Content

Firefox DevTools MCP is a Mozilla-maintained Model Context Protocol server for automating local Firefox through WebDriver BiDi and Selenium WebDriver. It lets Claude and other MCP clients inspect pages, navigate tabs, capture snapshots, interact with page elements by UID, collect network and console information, take screenshots, handle dialogs, adjust viewport size, restart Firefox, and optionally use script, privileged-context, preference, and WebExtension tools.

The project runs locally through npm and requires a local Firefox installation. It is intended for development, debugging, testing, and controlled browser automation rather than cloud-hosted MCP execution.

Source Review

These sources were reviewed on 2026-06-06. Prefer the live repository, README, npm metadata, package metadata, server entrypoint, tool exports, security policy, and license files for current install commands, Firefox requirements, tool behavior, risky flags, package naming, and licensing.

Features

  • Local stdio MCP server launched with npx -y firefox-devtools-mcp@latest.
  • Firefox automation through WebDriver BiDi and Selenium WebDriver.
  • Page tools for listing, creating, navigating, selecting, and closing pages.
  • Snapshot and UID workflows for element discovery and stable element actions.
  • Input tools for click, hover, fill, drag, form fill, and file upload.
  • Network request and console message inspection.
  • Screenshot tools for full-page or element-level captures.
  • Dialog, history, viewport, Firefox info, Firefox output, and restart tools.
  • Optional tools for JavaScript evaluation, privileged Firefox contexts, Firefox preferences, and WebExtension management.
  • Dual MIT or Apache-2.0 license, at the user's option.

Installation

Install and launch through npx:

npx -y firefox-devtools-mcp@latest

Configure your MCP client:

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

Use a clean Firefox profile for automation. Add documented flags such as --headless, --viewport, --profile-path, or --start-url only when needed, and avoid risky flags unless the environment is isolated.

Use Cases

  • Inspect a local web app with snapshots, screenshots, console messages, and network request details.
  • Navigate test pages and interact with elements through UID-based click, fill, drag, form-fill, and upload tools.
  • Debug Firefox-specific behavior without switching to another browser MCP server.
  • Capture browser logs, page screenshots, and network request evidence for a development note or issue.
  • Automate Firefox for Android workflows when adb and the target package are configured.
  • Use privileged context and preference tools only for browser-development or isolated Firefox debugging tasks.

Safety and Privacy

Browser automation gives an AI assistant access to whatever the controlled browser can reach. Use a dedicated Firefox profile, avoid sensitive sites, and assume web content can try to manipulate the agent through prompt injection in visible text, hidden markup, accessibility labels, console output, or network responses.

Keep optional capabilities narrow. JavaScript evaluation, privileged context access, Firefox preference changes, extension installation, insecure-certificate acceptance, and connect-existing mode all expand the risk surface. The upstream security guidance warns that privileged context with system access can cross normal web-content boundaries and should be used only in fully isolated environments.

Snapshots, screenshots, logs, headers, request URLs, file upload paths, extension lists, Firefox prefs, and browser state can expose credentials, customer data, private browsing context, local file names, or active sessions. Save screenshots and logs only to approved locations, and clear or discard dedicated profiles after sensitive test runs.

Duplicate Check

Existing content includes browser automation entries such as Playwright, Chrome DevTools, Browser MCP, and Browserbase. Firefox DevTools MCP is distinct because it covers mozilla/firefox-devtools-mcp, a Mozilla-maintained server for local Firefox automation through WebDriver BiDi with Firefox-specific profile, preference, privileged-context, extension, Android, and browser-management workflows. No dedicated Firefox DevTools MCP or Mozilla Firefox MCP entry was found in content/mcp.

#firefox#browser-automation#devtools#testing#web

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