Firefox MCP Server

This MCP server provides Firefox browser automation capabilities through Playwright, allowing you to control Firefox from within your MCP-enabled applications. Features both basic automation and advanced multi-tab debugging capabilities.

Features

Basic Automation

Launch Firefox browser (headless or visible)
Navigate to URLs
Click elements by selector or coordinates
Type text into input fields
Take screenshots
Get page content and text
Execute JavaScript
Browser navigation (back, forward, reload)
Wait for elements to appear

Multi-Tab Session Support

Create multiple isolated browser tabs with unique contexts
Independent session management for multiplayer testing
Switch between active tabs
List all active tabs
Close specific tabs

Advanced Debugging & Monitoring

Console Log Monitoring: Capture all console.log, error, warn, info, debug messages
JavaScript Error Tracking: Monitor unhandled errors and promise rejections with stack traces
WebSocket Traffic Monitoring: Real-time capture of WebSocket messages (perfect for Phoenix LiveView)
Network Activity Monitoring: HTTP requests/responses with headers and timing
Performance Metrics: DOM timing, paint events, memory usage tracking
Combined Debug Feed: Unified view of all debugging activity
Real-time Event Capture: Automatic monitoring without manual injection

Installation

Install dependencies:

npm install

Install Firefox browser for Playwright:

npx playwright install firefox

Configuration

Standard Configuration

Add this server to your MCP configuration file (usually ~/.config/mcp/cline.json or similar):

{
  "mcpServers": {
    "firefox-control": {
      "command": "node",
      "args": ["index.js"],
      "cwd": "/home/luke/workbench/drabardi/firefox-mcp-server"
    }
  }
}

Debug-Enhanced Configuration (Recommended)

For full debugging capabilities, use the enhanced server:

{
  "mcpServers": {
    "firefox-control": {
      "type": "stdio",
      "command": "node", 
      "args": ["/path/to/firefox-mcp-server/index-multi-debug.js"],
      "env": {"DISPLAY": ":1"}
    }
  }
}

Note: After updating configuration, restart Claude Code to activate new debug tools.

Available Tools

Basic Browser Control

launch_firefox_multi

Launch Firefox browser with multi-tab support and debugging

headless (boolean): Run in headless mode (default: false)
enableDebugLogging (boolean): Enable debug logging (default: true)

create_tab

Create a new tab with isolated session and debugging

tabId (string, required): Unique identifier for the tab
url (string): Initial URL to navigate to (default: "about")
enableMonitoring (boolean): Enable real-time monitoring (default: true)
contextId (string): Browser context ID for isolation

list_tabs

List all active tabs with their URLs and status

close_tab

Close a specific tab

tabId (string, required): Tab ID to close

set_active_tab

Set the active tab for subsequent operations

tabId (string, required): Tab ID to make active

navigate

Navigate to a URL

url (string, required): URL to navigate to
tabId (string): Specific tab to navigate (uses active tab if not specified)

click

Click on an element

selector (string): CSS selector to click
coordinates (object): Alternative - click at specific x,y coordinates
tabId (string): Target tab ID

type_text

Type text into an input field

selector (string, required): CSS selector of input field
text (string, required): Text to type
tabId (string): Target tab ID

send_key

Send keyboard events

key (string, required): Key to send
modifiers (array): Modifier keys (ctrl, shift, alt, meta)
repeat (number): Number of times to repeat (default: 1)
selector (string): Target element selector
tabId (string): Target tab ID

drag

Perform drag operation

selector (string): Element to drag
fromCoordinates (object): Starting coordinates {x, y}
toCoordinates (object): Ending coordinates {x, y}
offsetX (number): X offset for drag
offsetY (number): Y offset for drag
duration (number): Drag duration in ms (default: 0)
steps (number): Number of intermediate steps (default: 1)
tabId (string): Target tab ID

Content & Media

get_page_content

Get HTML content of the page

selector (string): Optional CSS selector for specific element
tabId (string): Target tab ID

get_page_text

Get visible text content of the page

selector (string): Optional CSS selector for specific element
tabId (string): Target tab ID

screenshot

Take a screenshot

path (string): File path to save screenshot (default: "screenshot.png")
fullPage (boolean): Capture full page (default: false)
tabId (string): Target tab ID

wait_for_element

Wait for an element to appear

selector (string, required): CSS selector to wait for
timeout (number): Timeout in milliseconds (default: 30000)
tabId (string): Target tab ID

execute_script

Execute JavaScript in the browser

script (string, required): JavaScript code to execute
tabId (string): Target tab ID

get_current_url

Get the current page URL

tabId (string): Target tab ID

back

Navigate back in browser history

tabId (string): Target tab ID

forward

Navigate forward in browser history

tabId (string): Target tab ID

reload

Reload the current page

tabId (string): Target tab ID

close_browser

Close the Firefox browser and all tabs

Advanced Debugging Tools

get_console_logs

Get captured console logs from browser

tabId (string): Target tab ID
limit (number): Max number of logs to return (default: 50)
since (number): Timestamp to filter logs since
types (array): Filter by log types ["log", "error", "warn", "info", "debug"]

get_javascript_errors

Get captured JavaScript errors

tabId (string): Target tab ID
limit (number): Max number of errors to return (default: 20)
since (number): Timestamp to filter errors since

get_network_activity

Get captured network requests and responses

tabId (string): Target tab ID
limit (number): Max number of requests to return (default: 30)
since (number): Timestamp to filter requests since
filter (string): Filter by request type ["all", "xhr", "websocket", "fetch"] (default: "all")

get_websocket_messages

Get captured WebSocket messages (perfect for LiveView debugging)

tabId (string): Target tab ID
limit (number): Max number of messages to return (default: 50)
since (number): Timestamp to filter messages since

get_performance_metrics

Get performance metrics (timing, memory usage)

tabId (string): Target tab ID

get_all_debug_activity

Get combined feed of all debug events

tabId (string): Target tab ID
limit (number): Max number of events to return (default: 100)
since (number): Timestamp to filter events since

inject_debugging_helpers

Inject debugging helper functions into the page

tabId (string): Target tab ID
includeWebSocketMonitoring (boolean): Include WebSocket monitoring (default: true)

start_monitoring

Start/restart monitoring for a tab

tabId (string): Target tab ID
types (array): Types to monitor ["console", "errors", "network", "websocket", "performance"] (default: all)

clear_debug_buffers

Clear debug event buffers for a tab

tabId (string): Target tab ID
types (array): Buffer types to clear ["console", "errors", "network", "websocket"]

Usage Examples

Basic Browser Automation

// Launch browser with debugging
mcp__firefox-control__launch_firefox_multi({headless: false, enableDebugLogging: true})

// Create tab and navigate
mcp__firefox-control__create_tab({tabId: "main", url: "https://example.com", enableMonitoring: true})

// Interact with page
mcp__firefox-control__click({selector: "button#submit", tabId: "main"})
mcp__firefox-control__type_text({selector: "input[name='search']", text: "hello world", tabId: "main"})

// Take screenshot
mcp__firefox-control__screenshot({path: "page.png", fullPage: true, tabId: "main"})

// Close
mcp__firefox-control__close_browser()

Multi-Player Game Testing

// Launch browser and create multiple player tabs
mcp__firefox-control__launch_firefox_multi({headless: false, enableDebugLogging: true})
mcp__firefox-control__create_tab({tabId: "player1", url: "http://localhost:4000/squid-ball", enableMonitoring: true})
mcp__firefox-control__create_tab({tabId: "player2", url: "http://localhost:4000/squid-ball", enableMonitoring: true})

// Player 1 creates game
mcp__firefox-control__set_active_tab({tabId: "player1"})
mcp__firefox-control__click({selector: 'button[phx-click="create_game"]', tabId: "player1"})

// Player 2 joins game (assuming game ID is available)
mcp__firefox-control__set_active_tab({tabId: "player2"})
mcp__firefox-control__type_text({selector: 'input[name="game_id"]', text: "GameID123", tabId: "player2"})
mcp__firefox-control__click({selector: 'button[type="submit"]', tabId: "player2"})

// Monitor both players independently
mcp__firefox-control__get_all_debug_activity({tabId: "player1", limit: 10})
mcp__firefox-control__get_all_debug_activity({tabId: "player2", limit: 10})

Phoenix LiveView Debugging

// Monitor WebSocket traffic for LiveView
mcp__firefox-control__get_websocket_messages({tabId: "player1", limit: 5})

// Get console logs with filtering
mcp__firefox-control__get_console_logs({tabId: "player1", types: ["error", "warn"], limit: 10})

// Monitor network activity
mcp__firefox-control__get_network_activity({tabId: "player1", filter: "xhr", limit: 20})

// Get performance metrics
mcp__firefox-control__get_performance_metrics({tabId: "player1"})

// Combined debug feed for comprehensive monitoring
mcp__firefox-control__get_all_debug_activity({tabId: "player1", limit: 50})

Real-time Game State Monitoring

// Capture real-time game ticks and delta state
mcp__firefox-control__get_websocket_messages({tabId: "player1", limit: 3})
// Returns: Ball position, paddle movement, tick numbers, player states

// Monitor console for LiveView updates
mcp__firefox-control__get_console_logs({tabId: "player1", types: ["log"], limit: 5})
// Returns: Phoenix LiveView update logs with game state changes

// Clear buffers and restart monitoring
mcp__firefox-control__clear_debug_buffers({tabId: "player1", types: ["console", "websocket"]})
mcp__firefox-control__start_monitoring({tabId: "player1", types: ["console", "websocket"]})

Use Cases

Game Development & Testing

Multiplayer Testing: Create multiple browser sessions to simulate different players
Real-time Debugging: Monitor WebSocket traffic, console logs, and game state changes
Client-side Prediction: Track timing and synchronization between client and server
Performance Monitoring: Measure frame rates, memory usage, and network latency

Phoenix LiveView Development

LiveView Debugging: Monitor Phoenix LiveView WebSocket messages and state updates
Real-time Applications: Track bidirectional communication and state synchronization
Error Tracking: Capture JavaScript errors and console warnings
Performance Analysis: Monitor DOM updates and rendering performance

Web Application Testing

Cross-tab Testing: Simulate multiple users in different browser contexts
Session Management: Test isolated sessions and user interactions
Network Monitoring: Track API calls, responses, and error handling
UI Testing: Automate interactions and capture screenshots

Requirements

Node.js 18+
Firefox (installed automatically by Playwright)
MCP-compatible client (Claude Code, etc.)
Display server for non-headless mode (DISPLAY environment variable)

Debugging Features

Automatic Monitoring

Console Logs: All console.log, error, warn, info, debug messages captured automatically
JavaScript Errors: Unhandled errors and promise rejections with full stack traces
WebSocket Traffic: Real-time capture of all WebSocket messages (send/receive)
Network Activity: HTTP requests/responses with headers, timing, and status codes
Performance Metrics: DOM timing, paint events, memory usage, and navigation timing

Data Filtering

Time-based Filtering: Filter events since a specific timestamp
Type Filtering: Filter console logs by type (error, warn, info, debug)
Network Filtering: Filter network requests by type (xhr, websocket, fetch)
Limit Control: Control the number of returned events to manage data volume

Multi-tab Support

Isolated Contexts: Each tab runs in its own browser context with independent debugging
Session Management: Maintain separate sessions for different users/players
Independent Monitoring: Each tab captures its own debug events without interference
Easy Switching: Switch between tabs for testing different user interactions

Architecture

Debug-Enhanced Server (`index-multi-debug.js`)

Built on Playwright for Firefox automation
Real-time event capture using Chrome DevTools Protocol
Independent monitoring per browser tab/context
Automatic buffer management with configurable limits
Event timestamping for precise debugging

Browser Context Isolation

Each tab gets its own browser context for complete isolation
Independent cookie storage, local storage, and session data
Separate network monitoring and debugging per context
No cross-contamination between different player sessions

Security Note

This server provides browser automation capabilities with extensive debugging access. Use with caution and ensure you trust the MCP client that will be controlling Firefox. The server can:

Execute arbitrary JavaScript in browser contexts
Monitor all network traffic and WebSocket messages
Access page content and user interactions
Take screenshots and access media devices

Install Server

HTTP connection URL

security – no known vulnerabilities

license - not found

quality - confirmed to work

How are these scores calculated?

local-only server

The server can only run on the client's local machine because it depends on local resources.

Tools

View all tools

Provides Firefox browser automation capabilities through Playwright, allowing control of Firefox from MCP-enabled applications with features for basic automation and advanced multi-tab debugging.

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