Local Browser MCP

A headless, agent-controllable real browser as an MCP server. It gives an AI agent (Claude Code, or any MCP client) a real Playwright browser pointed at your local dev servers — and any hosts you explicitly allow — with no VS Code and no GUI required. The agent launches the browser, drives it, and it's torn down when the session ends.

Navigate, click, hover, fill, type, run JS, screenshot, snapshot the DOM, and read console/network — all over MCP. Because it normally only drives your own localhost, it's given broad control without general-web-browsing risk; additional hosts are opt-in.

Install

Requires Node.js ≥ 18. The Chromium binary (~110 MB) is downloaded automatically on first install.

Claude Code / any MCP client (recommended)

Add it to your MCP config (e.g. a project .mcp.json, your user config via claude mcp add, or your client's equivalent). npx runs it straight from this GitHub repo — no npm registry account needed (requires git on the machine):

{
  "mcpServers": {
    "local-browser": {
      "command": "npx",
      "args": ["-y", "github:NolanLT/local-browser-mcp"],
      "env": {
        "LOCAL_BROWSER_ALLOWED_HOSTS": "localhost,127.0.0.1"
      }
    }
  }
}

Restart your client. The browser_* tools appear with no other setup. (First run installs dependencies and downloads Chromium, then caches.)

If the package is also published to npm, you can swap the arg for the shorter ["-y", "local-browser-mcp"].

As a Claude Code plugin (GitHub marketplace)

/plugin marketplace add NolanLT/local-browser-mcp
/plugin install local-browser@local-browser-marketplace

The plugin's MCP server is the same npx invocation above.

Configuration (environment variables)

| Variable | Default | Purpose | |----------|---------|---------| | LOCAL_BROWSER_ENGINE | chromium | chromium (recommended) | firefox | webkit | | LOCAL_BROWSER_ALLOWED_HOSTS | localhost,127.0.0.1 | Comma-separated navigation allowlist | | LOCAL_BROWSER_ALLOW_ALL | false | true allows any http/https host (see Security) | | LOCAL_BROWSER_SKIP_BROWSER_DOWNLOAD | — | 1 to skip the Chromium download on install | | LOCAL_BROWSER_HTTP_PORT | — | If set, run in HTTP mode on this port (else stdio) | | LOCAL_BROWSER_HTTP_HOST | 127.0.0.1 | HTTP bind address; use 0.0.0.0 for a directly-hosted box | | LOCAL_BROWSER_TOKEN | — | If set, HTTP requests need Authorization: Bearer <token> |

Remote / connector mode (claude.ai web & mobile, Cowork, Desktop connectors)

stdio only reaches clients on the same machine. To use this from claude.ai (web/mobile), Cowork, or a Desktop custom connector, run it in HTTP mode and expose it over public HTTPS — Anthropic's cloud connects to your endpoint, so it must be reachable and authenticated.

⚠️ A public endpoint can drive a real browser, including browser_eval. Always set LOCAL_BROWSER_TOKEN and keep a tight LOCAL_BROWSER_ALLOWED_HOSTS (and LOCAL_BROWSER_ALLOW_ALL=false) before exposing it. Without a token the HTTP path is unauthenticated.

Quick start (tunnel)

# 1. Generate a secret and run in HTTP mode
export LOCAL_BROWSER_TOKEN=$(openssl rand -hex 32)
LOCAL_BROWSER_HTTP_PORT=3000 node dist/server.cjs
#   → [local-browser] HTTP MCP ready on http://127.0.0.1:3000/mcp

# 2. In another shell, expose it over public HTTPS (TLS terminates at the tunnel)
cloudflared tunnel --url http://127.0.0.1:3000     # or: ngrok http 3000
#   → https://something.trycloudflare.com

Then register the connector in claude.ai (also Desktop/Cowork): Customize → Connectors → "+" → name it, enter the public https://…/mcp URL, and put your token in the auth/Bearer field → Add → enable it per-conversation via the "+" in the composer.

Production (always-on)

Host on a box that can run Chromium (VPS, Fly.io, Render, a Playwright-deps container — not serverless edge, which can't spawn Chromium). Set LOCAL_BROWSER_HTTP_HOST=0.0.0.0, keep LOCAL_BROWSER_TOKEN on, and terminate TLS at a reverse proxy (Caddy/nginx) or pass real certs.

GET /health is always open (no secrets) for setup checks; everything else requires the token.

Tools

| Tool | Purpose | |------|---------| | browser_navigate({ url }) | Go to a URL (allowlist-validated) | | browser_screenshot({ fullPage?, selector? }) | PNG returned to the agent | | browser_snapshot() | Flat DOM/a11y snapshot { tag, role, text, ref } | | browser_click({ selector \| ref }) | Click an element | | browser_hover({ selector \| ref }) | Hover (e.g. open a dropdown) | | browser_fill({ selector, value }) | Fill an input | | browser_type({ text }) | Type into the focused element | | browser_eval({ expression }) | Run JS in the page, return JSON result | | browser_console() / browser_network() | Buffered console / recent requests | | browser_wait_for({ selector?, text?, timeoutMs? }) | Wait for a condition | | browser_resize({ width, height }) | Resize the viewport | | browser_reload() / browser_back() / browser_forward() | History nav | | browser_get_text() | Visible page text | | browser_allow_host / browser_disallow_host / browser_list_allowed | Allowlist management |

ref values come from browser_snapshot() (elements are tagged with data-lbmcp-ref), so browser_click({ ref }) targets them reliably.

Security

Navigation is rejected unless the host is in LOCAL_BROWSER_ALLOWED_HOSTS (or ALLOW_ALL is on) and the protocol is http/https.
The browser uses a fresh, ephemeral profile — no saved cookies, logins, or passwords.
browser_eval runs arbitrary JS with the page's full privileges. Harmless on your own dev site; powerful on a real one. With ALLOW_ALL on, every visited page is untrusted input (prompt- injection surface) and the agent can script it — keep ALLOW_ALL off unless you mean it.
There's no built-in approval dialog (the server is headless). When run under Claude Code, host additions and eval calls are gated by Claude Code's own per-tool permission prompts.
In HTTP mode there is no per-call prompt — the bearer token (LOCAL_BROWSER_TOKEN) is the gate. Set it before exposing the endpoint publicly, and keep the host allowlist tight. See Remote / connector mode.

Develop

npm install        # installs deps + downloads Chromium
npm run typecheck  # tsc --noEmit
npm run build      # bundle → dist/server.cjs

Run it directly for a stdio smoke test:

node dist/server.cjs

See CONTRIBUTING.md for the full dev/release workflow.

Project

License

MIT

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