chrome-fast

Fast Chrome browser automation MCP server (stdio or HTTP) backed by the Chrome DevTools Protocol. It drives a real, logged-in Chrome profile and returns pages as a compact accessibility tree with numbered element refs, so an agent can read, click, type and fill forms with very few round trips.

Setup on a new PC

Prerequisites

• Node.js 20+

• Google Chrome installed

Install

npm install
npm run build

Start Chrome in debug mode

Double-click start-chrome-debug.bat. It opens Chrome on port 9222 with an isolated profile under %LOCALAPPDATA%\NanoClaw\ChromeProfile. Sign in to any accounts you need (e.g. Google for Gemini) in that window; the profile persists.

You only need the bat for the first run (to sign in). After that chrome-fast launches Chrome itself: whenever a tool is called and nothing is listening on the debug port, it starts Chrome with the same flags and the same profile, waits for the port, then connects.

Environment variables (all optional):

The bat script honours CHROME_PORT, CHROME_PROFILE, CHROME_PATH and CHROME_DEBUG_ADDRESS too.

Register in Claude Code (~/.claude.json)

Stdio mode (recommended for single-machine use):

{
  "mcpServers": {
    "chrome-fast": {
      "command": "node",
      "args": ["C:\\path\\to\\chrome-fast\\dist\\index.js"]
    }
  }
}

HTTP mode (for containers / cross-machine):

node dist/index.js --http 3500

This serves two transports on the same port:

• http://localhost:3500/mcp — Streamable HTTP, the current MCP transport (claude mcp add --transport http chrome-fast http://host.docker.internal:3500/mcp)

• http://localhost:3500/sse — the older HTTP+SSE transport, for clients that still need it

• http://localhost:3500/health — returns ok

The HTTP server gives anyone who can reach it full control of the browser. Set MCP_HTTP_TOKEN when the port is reachable from other machines and pass the token from the client, e.g. claude mcp add --transport http chrome-fast http://host:3500/mcp --header "Authorization: Bearer <token>".

Verify

Restart Claude Code. The mcp__chrome-fast__* tools should be available. Try:

• mcp__chrome-fast__tabs — lists open Chrome tabs

• mcp__chrome-fast__navigate — navigates a tab

Test

npm run build
npm test

The end-to-end test launches a headless Chrome with a throwaway profile, serves fixture pages locally and exercises every tool. It needs Chrome installed (or CHROME_PATH set).

Related MCP server: agent-chrome

Tools provided

• navigate (url, waitUntil: load / domcontentloaded / networkidle, timeout)

• tabs, tab_new, tab_switch, tab_close

• get_page (format: accessibility with page text, interactive without text, or html), screenshot, evaluate

• click, type, scroll, fill_form

• wait (CSS selector, text on the page, network idle, or a fixed time)

Notes for drivers

• Element refs returned by get_page / navigate / click / type are plain numbers (pass "55"). They go stale when the page re-renders; if a tool reports a stale ref, call get_page again.

• Snapshots list the page text as text "…" lines, headings with their level, and form fields with their current value="…". Lines starting with Note: report things handled automatically, for example a dismissed confirm() dialog or a page that did not finish loading in time.

• click scrolls the element into view first. If another element covers it, a DOM click() is dispatched instead and a note says so. When a click starts a navigation, the new page is returned.

• type appends to the existing content; use clear: true to replace it. pressEnter: true submits forms and sends chat prompts (Gemini, for example).

• fill_form handles text inputs, textareas, <select> (by option value or label), checkboxes and radios ("true" / "false") and contenteditable elements, in a way React and similar frameworks notice. submit: true submits the form like its submit button would (validation and submit handlers run).

• JavaScript dialogs never block the tools: alert and beforeunload are accepted, confirm and prompt are dismissed. To accept a confirm, run evaluate with window.confirm = () => true first.

• evaluate behaves like the DevTools console: top-level await, several statements, let that can be declared again on the next call, and the $ / $$ helpers. Promises are awaited, DOM nodes come back as HTML, and objects as JSON. It stops after 30 seconds.

• screenshot returns a PNG (or JPEG) image block; fullPage: true captures the whole scrollable page, scaled down if it would exceed what the Claude API accepts.