OpenChrome

Harness-Engineered Browser Automation
The MCP server that guides AI agents.

How OpenChrome compares

tl;dr — OpenChrome talks directly to Chrome via CDP with zero middleware, reuses your real login sessions, and is the only browser MCP server with harness engineering — 27 intelligent subsystems that guide, protect, and optimize the AI agent at every step.

What is OpenChrome?

Imagine 20+ parallel Playwright sessions — but already logged in to everything, invisible to bot detection, and sharing one Chrome process at 300MB. That's OpenChrome.

Search across 20 sites simultaneously. Crawl authenticated dashboards in seconds. Debug production UIs with real user sessions. Connect to OpenClaw and give your AI agent browser superpowers across Telegram, Discord, or any chat platform.

You: oc compare "AirPods Pro" prices across Amazon, eBay, Walmart,
     Best Buy, Target, Costco, B&H, Newegg — find the lowest

AI:  [8 parallel workers, all sites simultaneously]
     Best Buy:  $179 ← lowest (sale)
     Amazon:    $189
     Costco:    $194 (members)
     ...
     Time: 2.8s | All prices from live pages, already logged in.

Harness-Engineered, Not Just Automated

Traditional browser automation exposes raw APIs. When the AI agent fails, it's on its own — burning tokens guessing, retrying, and wandering. Harness engineering means the tool itself wraps intelligence around those APIs: preventing mistakes, recovering from errors, and guiding the agent toward efficient behavior.

The bottleneck in browser automation isn't the browser — it's the LLM thinking between each step. Every tool call costs 5–15 seconds of inference time. When an AI agent guesses wrong, it doesn't just fail — it spends another 10 seconds thinking about why, then another 10 seconds trying something else.

Playwright agent checking prices on 5 sites:

  Site 1:  launch browser           3s
           navigate                  2s
           ⚡ bot detection          LLM thinks... 12s → retry with UA
           ⚡ CAPTCHA                LLM thinks... 10s → stuck, skip
           navigate to login         2s
           ⚡ no session             LLM thinks... 12s → fill credentials
           2FA prompt               LLM thinks... 10s → stuck
           ...
           finally reaches product   after ~20 LLM calls, ~4 minutes

  × 5 sites, sequential  =  ~100 LLM calls,  ~20 minutes,  ~$2.00

  Actual work: 5 calls.  Wasted on wandering: 95 calls.

OpenChrome eliminates this entirely — your Chrome is already logged in, and the hint engine corrects mistakes before they cascade:

OpenChrome agent checking prices on 5 sites:

  All 5 sites in parallel:
    navigate (already authenticated)     1s
    read prices                          2s
    ⚡ stale ref on one site
      └─ Hint: "Use read_page for fresh refs"    ← no guessing
    read_page → done                     1s

  = ~20 LLM calls,  ~15 seconds,  ~$0.40

The hint engine watches every tool call across 9 categories — error recovery, blocking page detection, composite suggestions, repetition detection, sequence detection, pagination detection, learned patterns, success guidance, and setup hints. When it sees the same error→recovery pattern 3+ times, it promotes it to a permanent rule across sessions via the Pattern Learner.

27 Harness Features Across 7 Categories

OpenChrome isn't just a browser API — it's an intelligent harness with 27 subsystems that work together:

Desktop App (Beta)

OpenChrome is also available as a desktop app — a one-click installer that runs the MCP server locally without requiring Node.js, npm, or any command-line setup. Designed for non-developers who want browser automation without the terminal.

Note: These are unsigned builds. See installation notes below.

Download

Get Started (non-developers)

1. Download the installer for your platform from the Releases page.
2. Install — open the .dmg / run the .exe installer / make the .AppImage executable and launch it.
3. Connect — the app starts the MCP server automatically. Point your MCP client (Claude, Cursor, etc.) to the local server address shown in the app.

Installation Notes

macOS: The app is not notarized. On first launch, macOS will block it. To fix:

xattr -cr /Applications/OpenChrome.app

Or right-click the app → Open → Open.

Windows: SmartScreen will show "Windows protected your PC". Click "More info" → "Run anyway".

Linux: No additional steps needed. Download the AppImage, make it executable (chmod +x), and run.

Note: The desktop app and the CLI (openchrome-mcp on npm) are separate distributions with independent version numbers. You do not need both — use whichever fits your workflow. See desktop/RELEASING.md for the desktop release process.

Quick Start

Claude Code

npx openchrome-mcp setup

Codex CLI

npx openchrome-mcp setup --client codex

One command. Configures the MCP server for the selected client. Restart your MCP client after setup completes.

claude mcp add openchrome -- npx -y openchrome-mcp@latest serve --auto-launch

{
  "servers": {
    "openchrome": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "openchrome-mcp@latest", "serve", "--auto-launch"]
    }
  }
}

{
  "mcpServers": {
    "openchrome": {
      "command": "npm",
      "args": ["exec", "--yes", "--prefer-online", "openchrome-mcp@latest", "--", "serve", "--auto-launch"]
    }
  }
}

{
  "mcpServers": {
    "openchrome": {
      "command": "npx",
      "args": ["-y", "openchrome-mcp@latest", "serve", "--auto-launch"]
    }
  }
}

Examples

Parallel monitoring:

oc screenshot AWS billing, GCP console, Stripe, and Datadog — all at once
→ 4 workers, 3.1s, already authenticated everywhere

Multi-account:

oc check orders on personal and business Amazon accounts simultaneously
→ 2 workers, isolated sessions, same site different accounts

Competitive intelligence:

oc compare prices for "AirPods Pro" across Amazon, eBay, Walmart, Best Buy
→ 4 workers, 4 sites, 2.4s, works past bot detection

46 Tools

CLI

oc setup                    # Auto-configure
oc serve --auto-launch      # Start server
oc serve --headless-shell   # Headless mode
oc doctor                   # Diagnose issues

Cross-Platform

DOM Mode (Token Efficient)

read_page supports three output modes:

DOM mode example:

read_page tabId="tab1" mode="dom"

[page_stats] url: https://example.com | title: Example | scroll: 0,0 | viewport: 1920x1080

[142]<input type="search" placeholder="Search..." aria-label="Search"/> ★
[156]<button type="submit"/>Search ★
[289]<a href="/home"/>Home ★
[352]<h1/>Welcome to Example

DOM mode outputs [backendNodeId] as stable identifiers — they persist for the lifetime of the DOM node, unlike ref_N IDs which are cleared on each AX-mode read_page call.

Stable Selectors

Action tools that accept a ref parameter (form_input, computer, etc.) support three identifier formats:

Backward compatible — existing ref_N workflows work unchanged. DOM mode's backendNodeId eliminates "ref not found" errors caused by stale references.

Session Persistence

Headless mode (--headless-shell) doesn't persist cookies across restarts. Enable storage state persistence to maintain authenticated sessions:

oc serve --persist-storage                         # Enable persistence
oc serve --persist-storage --storage-dir ./state    # Custom directory

Cookies and localStorage are saved atomically every 30 seconds and restored on session creation.

Anti-Bot & Turnstile Support

OpenChrome includes built-in defenses against Cloudflare Turnstile and similar anti-bot systems. See Turnstile Guide for details.

3-Tier Auto-Fallback for CDN/WAF Blocks

When a navigation is blocked by CDN/WAF systems (Akamai, Cloudflare, etc.), OpenChrome automatically escalates through three tiers:

Tier 3 launches a real headed Chrome window with a genuine user-agent (Chrome/... instead of HeadlessChrome/...) and a different TLS fingerprint, bypassing binary-level detection that no JavaScript injection can fix.

Parameters:

• autoFallback: false — disable all automatic retry
• headed: true — skip directly to Tier 3 (headed Chrome)
• stealth: true — use stealth mode (Tier 2) explicitly

Environment: Tier 3 requires a display (macOS/Windows desktop, or Linux with $DISPLAY). In server/container environments without a display, Tier 3 is gracefully skipped.

Known Limitations

• CAPTCHA-protected sites (e.g., Reddit): Auto-fallback correctly detects and escalates through all tiers, but sites that serve CAPTCHA challenges ("Prove your humanity") to all automated clients — regardless of headless/headed mode — require human interaction to solve. This is beyond auto-fallback's scope, which targets CDN/WAF network-level blocking (TLS fingerprint, user-agent detection), not interactive CAPTCHA challenges.

FAQ: Comparison with Other Browser MCPs

Common questions from users evaluating OpenChrome against Chrome DevTools MCP, Firefox DevTools MCP, and similar tools (see #612).

Can multiple MCP clients share tabs safely?

Yes — tabs cannot clobber each other across clients.

OpenChrome identifies every tab by its CDP targetId — a stable, browser-assigned string — not by a visible 1/2/3 index. On top of stable IDs, two layers of isolation are specifically designed for multi-client scenarios:

• workerId — logical tab groups per client or parallel lane. A new tab under one workerId is invisible to another and never replaces one.
• profileDirectory — launches a fully separate Chrome instance bound to that profile, giving OS-level cookie / storage / extension isolation.

If client A opens five tabs and client B opens five tabs, all ten tabIds are distinct and stable; a new tab from A can never displace B's tab #3.

How do I handle sites that require interactive login (password, 2FA, CAPTCHA)?

Two mechanisms, used together in practice:

1. Persistent-profile headless — log in once, automate forever. Point OpenChrome at a persistent userDataDir (+ optional profileDirectory) and cookies / localStorage / IndexedDB survive across runs. After the first login, subsequent headless runs stay logged in until the site invalidates the session.

2. Headed fallback for the initial login or WAF-blocked sites. When a human action is genuinely required (first-time login, 2FA, CAPTCHA, WebAuthn) or when a Tier-1/Tier-2 headless attempt is blocked by a CDN/WAF, OpenChrome lazy-launches a separate headed Chrome on a different debug port. Cookies are sync'd from the real Chrome profile before launch, and the headed page is registered back into the same logical session so the surrounding workflow continues seamlessly.

Typical pattern: bootstrap the login once via the headed path → the persistent profile carries the cookies → all subsequent automation runs headless without a window.

Does OpenChrome steal focus with popup windows?

No — the "recurring popup interruptions" problem does not occur in OpenChrome.

The headed-browser focus-stealing pattern that users encounter with some MCP servers (cross-Space jumps on macOS, un-minimizable popups, per-tool-call window raises) comes from designs where the MCP drives a user-visible browser and creates OS windows as it works. OpenChrome is architected differently:

• Default mode is headless — no window exists, so there is nothing to take focus.
• tabs_create opens a tab, not an OS window. New tabs are created via CDP inside the already-running Chrome, and OpenChrome never calls page.bringToFront() anywhere in the codebase.
• The headed fallback is lazy and reused. When it is needed, it launches once per server lifetime; every later navigation/tab runs inside that same instance. At worst you see one focus grab the very first time the fallback activates — not one per action, never one per tab.
• The headed fallback is optional. If persistent-profile headless is sufficient for your sites, you will never see a browser window.

The only scenario in which a window appears at all is the first time the Tier-3 headed fallback activates in a given session.

Benchmarks

Measure token efficiency and parallel performance:

npm run benchmark                                    # Stub mode: AX vs DOM token efficiency (interactive)
npm run benchmark:ci                                 # Stub mode: AX vs DOM with JSON + regression detection
npm run benchmark -- --mode real                     # Real mode: actual MCP server (requires Chrome)
npx ts-node tests/benchmark/run-parallel.ts          # Stub mode: all parallel benchmark categories
npx ts-node tests/benchmark/run-parallel.ts --mode real --category batch-js --runs 1  # Real mode
npx ts-node tests/benchmark/run-parallel.ts --mode real --category realworld --runs 1  # Real-world benchmarks

By default, benchmarks run in stub mode — measuring protocol correctness and tool-call counts with mock responses. Use --mode real to spawn an actual MCP server subprocess and measure real performance (requires Chrome to be available).

Parallel benchmark categories:

Server / Headless Deployment

OpenChrome works on servers and in CI/CD pipelines without Chrome login. All 46 tools function with unauthenticated Chrome — navigation, scraping, screenshots, form filling, and parallel workflows all work in clean sessions.

Quick start

# Single flag for optimal server defaults
openchrome serve --server-mode

--server-mode automatically sets:

• Auto-launches Chrome in headless mode
• Skips cookie bridge scanning (~5s faster per page creation)
• Optimal defaults for server environments

What works without login

Important: MCP client required

OpenChrome is an MCP server — it responds to tool calls, not standalone scripts. Server-side usage requires an MCP client (e.g., Claude API, Claude Code, or a custom MCP client) to drive it:

MCP Client (LLM) → stdio → OpenChrome (--server-mode) → Chrome

For standalone scraping scripts without an LLM, use Playwright or Puppeteer directly.

Docker

A production-ready Dockerfile is included in the repository:

docker build -t openchrome .
docker run openchrome

Environment variables

Individual flags

For fine-grained control, use individual flags instead of --server-mode:

openchrome serve \
  --auto-launch \
  --headless-shell \
  --port 9222

Authentication

OpenChrome supports per-tenant API keys, JWT/OAuth, a legacy shared token, and an unauthenticated mode. See docs/auth.md for the full guide including quickstart, scope table, key rotation, revocation, and troubleshooting.

Under the Hood: 8-Layer Reliability

OpenChrome has 49 distinct reliability mechanisms across 8 defense layers — ensuring no single failure can hang the MCP server.

┌─────────────────────────────────────────────────────────────┐
│  Layer 7: MCP Gateway                                       │
│  Rate limiter · Tool timeout (120s) · Error recovery hints  │
├─────────────────────────────────────────────────────────────┤
│  Layer 6: Session Management                                │
│  TTL cleanup · Memory pressure · Target reconciliation      │
├─────────────────────────────────────────────────────────────┤
│  Layer 5: Request Queue                                     │
│  Per-session FIFO · Per-item timeout (120s)                 │
├─────────────────────────────────────────────────────────────┤
│  Layer 4: Circuit Breaker                                   │
│  Element (3 fails) · Page (5 fails) · Global (10/5min)     │
├─────────────────────────────────────────────────────────────┤
│  Layer 3: CDP Client                                        │
│  Adaptive heartbeat · Stale target guard · Page defenses    │
├─────────────────────────────────────────────────────────────┤
│  Layer 2: Reconnection Engine                               │
│  Auto-reconnect (5 retries) · Exponential backoff · Cookie  │
│  restore · Sleep/wake detection                             │
├─────────────────────────────────────────────────────────────┤
│  Layer 1: Self-Healing                                      │
│  Chrome watchdog · Tab health monitor · Event loop monitor  │
│  Disk monitor · Health endpoint (/health, /metrics)         │
├─────────────────────────────────────────────────────────────┤
│  Layer 0: Process Lifecycle                                 │
│  Graceful shutdown · Orphan cleanup · Atomic file writes    │
└─────────────────────────────────────────────────────────────┘

32 configurable timeouts cover every operation from CDP commands (15s) to tool execution (120s) to Chrome launch (60s). Every timeout is independently tunable via src/config/defaults.ts.

Element Intelligence

Finding elements by natural language instead of CSS selectors:

"Submit button" → normalizeQuery → parseQueryForAX → AX Tree Resolution
                                                          │
                                                     match found?
                                                     /         \
                                                   yes          no
                                                    │            │
                                              [AX result]   CSS Fallback
                                                             + Shadow DOM
                                                             + Scoring

• AX-first: Uses Chrome's accessibility tree — framework-agnostic across React, Angular, Vue, Web Components
• Cascading filter: 4-level deterministic priority (exact role+name → role+contains → exact name → partial)
• 3-tier Shadow DOM: Open roots (JS) + closed roots (CDP) + user-agent roots
• Hit detection: After clicking, reports what was actually hit + nearest interactive element
• i18n: Korean role keywords built-in ("버튼" → button, "링크" → link, "드롭다운" → combobox)

Development

git clone https://github.com/shaun0927/openchrome.git
cd openchrome
npm install && npm run build && npm test

License

MIT