even-better-playwright-mcp

The best of all worlds Playwright MCP server - combining intelligent DOM compression, code execution, visual labels, and advanced DevTools capabilities.

Features

• 🎭 Full Playwright API - Execute any Playwright code via the execute tool
• 🏗️ 90%+ DOM Compression - SimHash-based list folding and wrapper removal
• 📍 Ref-Based Elements - Stable [ref=e1] identifiers with aria-ref selectors
• 🔍 Regex Search - Find content in snapshots without re-fetching
• 🎯 Visual Labels - Vimium-style overlays for screenshot-based interaction
• 🔧 Advanced DevTools - Debugger, live editor, styles inspection, React source finding
• 🔒 Sandboxed Execution - Safe VM with scoped file system and module allowlist

Installation

npm install -g even-better-playwright-mcp

Or use directly with npx:

npx even-better-playwright-mcp

Configuration

Add to your MCP client settings (e.g., Claude Desktop's claude_desktop_config.json):

{
  "mcpServers": {
    "playwright": {
      "command": "npx",
      "args": ["even-better-playwright-mcp"]
    }
  }
}

CLI Options

Usage: even-better-playwright-mcp [options]

Options:
  --browser <browser>       Browser to use: chromium, firefox, webkit (default: chromium)
  --headless               Run browser in headless mode (default: false)
  --cdp-endpoint <url>     Connect to existing browser via CDP endpoint
  --user-data-dir <path>   Use persistent browser profile directory
  -h, --help               Show help message

Examples

# Basic usage (launches Chromium in headed mode)
even-better-playwright-mcp

# Use Firefox in headless mode
even-better-playwright-mcp --browser firefox --headless

# Connect to existing Chrome instance
even-better-playwright-mcp --cdp-endpoint ws://localhost:9222

# Use persistent profile
even-better-playwright-mcp --user-data-dir ./browser-profile

Tools

1. snapshot - Get Page Structure

Get compressed accessibility snapshot with ref IDs for element targeting.

Returns: DOM tree with [ref=e1], [ref=e2] etc.
Use refs with execute tool: await $('e1').click()
Call again after navigation (refs become stale).

Options:

• compress (boolean, default: true) - Enable smart compression (~90% token reduction)

Example output:

### Page Info
- URL: https://example.com
- Title: Example Domain

### Accessibility Snapshot
- document [ref=e1]
  - heading "Example Domain" [level=1] [ref=e2]
  - paragraph [ref=e3]: This domain is for use in illustrative examples...
  - link "More information..." [ref=e4]

2. browser_execute - Run Playwright Code

Execute any Playwright code with full API access. This is the main tool for browser automation.

Scope variables:

• page - Current Playwright page
• context - Browser context
• state - Persistent object across calls
• $('e5') - Shorthand for page.locator('aria-ref=e5')
• accessibilitySnapshot() - Get current page snapshot

Common patterns:

// Navigate
await page.goto('https://example.com')

// Click by ref (from snapshot)
await $('e5').click()

// Fill input
await $('e12').fill('search query')

// Get text
const text = await $('e3').textContent()

// Wait for network
await page.waitForLoadState('networkidle')

// Screenshot
await page.screenshot({ path: 'screenshot.png' })

Advanced - DevTools access:

// Get CDP session for debugging
const cdp = await getCDPSession({ page })
const dbg = createDebugger({ cdp })

// Set breakpoint
await dbg.setBreakpoint({ file: 'app.js', line: 42 })

// Inspect styles
const styles = await getStylesForLocator({ locator: $('e5') })

// Find React component source
const source = await getReactSource({ locator: $('e5') })
// => { fileName: 'Button.tsx', lineNumber: 42 }

Safe modules via require(): path, url, crypto, buffer, util, assert, os, fs (sandboxed)

3. screenshot - Capture Page Image

Capture screenshots with optional visual ref labels.

Options:

• ref (string) - Screenshot specific element by ref
• fullPage (boolean) - Capture entire scrollable area
• withLabels (boolean) - Show Vimium-style ref labels

Label colors by role:

4. browser_search_snapshot - Search Content

Search the last captured snapshot using regex patterns.

Options:

• pattern (string) - Regex pattern to search for
• ignoreCase (boolean, default: false) - Case-insensitive matching
• lineLimit (number, default: 100) - Maximum lines to return

Example:

Pattern: "button|link"
Result: 
- link "Contact Us" [ref=e15]
- button "Submit" [ref=e23]
- link "Privacy Policy" [ref=e31]

Workflow

Basic Automation

1. Get page structure

   Use: snapshot tool
   → See all interactive elements with refs
   

2. Interact with elements

   Use: execute tool
   Code: await $('e5').click()
   

3. After navigation, refresh refs

   Use: snapshot tool again
   → Refs are stale after navigation
   

Visual Automation

1. Take labeled screenshot

   Use: screenshot tool with withLabels: true
   → See visual labels overlaid on elements
   

2. Identify element from image

   Label shows: "e5" on a button
   

3. Click using ref

   Use: execute tool
   Code: await $('e5').click()
   

Architecture

┌─────────────────────────────────────────────────────────────────┐
│                     even-better-playwright-mcp                  │
├─────────────────────────────────────────────────────────────────┤
│  CORE                                                           │
│  ├── aria-ref selector system ([ref=e1], [ref=e2], etc.)       │
│  ├── page._snapshotForAI() for accessibility snapshots         │
│  └── Standard Playwright browser automation                     │
├─────────────────────────────────────────────────────────────────┤
│  ENHANCED SNAPSHOT                                              │
│  ├── SimHash-based list folding (compress 48 items → 2 lines)  │
│  ├── Useless wrapper removal                                    │
│  └── Regex-powered content search                               │
├─────────────────────────────────────────────────────────────────┤
│  CODE EXECUTION                                                 │
│  ├── browser_execute tool (run Playwright code in VM sandbox)  │
│  ├── Sandboxed require (safe module allowlist)                  │
│  ├── Scoped file system (cwd, /tmp only)                       │
│  └── Console log capture and forwarding                         │
├─────────────────────────────────────────────────────────────────┤
│  ADVANCED DEVTOOLS                                              │
│  ├── Debugger class (breakpoints, step, inspect variables)     │
│  ├── Editor class (live code editing without reload)           │
│  ├── Styles inspection (CSS like DevTools panel)               │
│  └── React source finding (component file/line locations)      │
├─────────────────────────────────────────────────────────────────┤
│  VISUAL OVERLAYS                                                │
│  ├── Vimium-style labels on interactive elements               │
│  ├── Color-coded by role (links=yellow, buttons=orange, etc.)  │
│  └── Screenshot with visible ref labels                         │
└─────────────────────────────────────────────────────────────────┘

Ref System

All projects use the same ref system built into Playwright:

• Snapshots generate refs like [ref=e1]
• Selectors use page.locator('aria-ref=e1')
• Shorthand $('e1') in execute tool

Important: Refs become stale after navigation. Always call snapshot again after page.goto() or clicking links that navigate.

Compression Algorithm

The snapshot compression achieves ~90% token reduction:

Original DOM (5000+ lines)
    ↓ removeUselessWrappers()
    ↓ truncateText(50 chars)
    ↓ detectSimilarPatterns(SimHash)
    ↓ foldLists()
Compressed (<500 lines)

Example:

Before:
- listitem [ref=e234]: Product 1 - Description...
- listitem [ref=e235]: Product 2 - Description...
- listitem [ref=e236]: Product 3 - Description...
... (48 items)

After:
- listitem [ref=e234]: Product 1 - Description...
- listitem (... and 47 more similar) [refs: e235, e236, ...]

Error Handling

The execute tool provides contextual hints:

• Stale ref: "Page may have navigated. Refs are stale after navigation. Call snapshot tool to get fresh refs."
• Timeout: "Operation timed out. Try increasing timeout or check if element exists/is visible."
• Hidden element: "Element may be hidden or covered by another element. Try scrolling or closing overlays."
• Connection lost: "Browser connection lost. The browser may have been closed - try again to relaunch."

Development

Building from Source

git clone https://github.com/your-repo/even-better-playwright-mcp
cd even-better-playwright-mcp
npm install
npm run build

Project Structure

even-better-playwright-mcp/
├── bin/
│   └── cli.ts              # CLI entry point with arg parsing
├── src/
│   ├── index.ts            # MCP server setup
│   ├── browser.ts          # Browser/context management
│   ├── vm-context.ts       # VM sandbox setup
│   ├── tools/
│   │   ├── snapshot.ts     # Snapshot tool (compressed)
│   │   ├── execute.ts      # Execute tool (main)
│   │   ├── screenshot.ts   # Screenshot tool (with labels)
│   │   └── search.ts       # Search tool
│   ├── utils/
│   │   ├── smart-outline.ts    # DOM compression
│   │   ├── list-detector.ts    # Pattern detection
│   │   ├── dom-simhash.ts      # SimHash implementation
│   │   ├── scoped-fs.ts        # Sandboxed file system
│   │   └── search.ts           # Regex search
│   ├── devtools/
│   │   ├── cdp-session.ts      # CDP connection
│   │   ├── debugger.ts         # Debugger class
│   │   ├── editor.ts           # Live editor
│   │   ├── styles.ts           # CSS inspection
│   │   └── react-source.ts     # React locations
│   └── visual/
│       └── aria-labels.ts      # Vimium-style overlays
├── package.json
├── tsconfig.json
└── README.md

Acknowledgments

This project combines the best ideas from:

• better-playwright-mcp - Intelligent DOM compression
• playwriter - Code execution and DevTools
• playwright-mcp - Microsoft's official MCP

License

MIT