chrome-mcp

Drive a real Chrome browser from Claude (or any MCP host). An MV3 extension drives your real Chrome — real logins, real cookies — via chrome.scripting/chrome.tabs. The CLI runs a localhost WebSocket server; the extension dials in.

Distributed as an npx CLI (the MCP server) plus a load-unpacked extension.

This build is extension-only. It never launches or attaches a Chromium of its own, so the extension is required, not optional — without it, no tool can run. The CDP flags (--cdp-fallback, --no-cdp-fallback, --cdp-endpoint, --prefer) are still accepted for back-compat but are ignored.

Full design: docs/BLUEPRINT.md — architecture, wire protocol, the complete tool surface, the extension manifest, the security model, and the phased build plan.

Quickstart

1. Register the MCP server with your host (e.g. Claude Desktop / Code):

{
  "mcpServers": {
    "chrome-mcp": {
      "command": "npx",
      "args": ["-y", "@mehmoodqureshi/chrome-mcp", "--allow-domain", "example.com", "--enable-mutations"]
    }
  }
}

By default everything is deny-all (no domains, no eval, no mutations). Grant exactly what you need with --allow-domain <glob> (repeatable), --enable-mutations, --enable-downloads, --enable-uploads, --unsafe-enable-eval, or --unsafe-all-domains.

--enable-uploads permits upload_file (setting local file(s) on a page's file <input>). It is off by default because sending local files to a page is an exfiltration risk; it is also gated by the destination-domain allowlist. Pair it with --uploads-dir <path> to restrict uploads to files inside that directory (.. traversal is blocked) — strongly recommended for unattended use.

Pair once, never again. Add --persist-token so the pairing token survives restarts:

{
  "mcpServers": {
    "chrome-mcp": {
      "command": "npx",
      "args": ["-y", "@mehmoodqureshi/chrome-mcp",
               "--allow-domain", "example.com", "--enable-mutations",
               "--persist-token"]
    }
  }
}

Without --persist-token a fresh token is minted every boot (the secure default), which means re-pairing the extension on each restart. With it, the token is stored 0600 at ~/.chrome-mcp/token and reused; the extension's keepalive auto-reconnects with no manual step. CHROME_MCP_TOKEN pins the token explicitly (and is never written to disk).

2. Load the extension — required; the server can drive nothing without it.

extension-dist/ ships prebuilt inside the npm package, so there is nothing to compile. Install globally to get a stable path to it:

npm install -g @mehmoodqureshi/chrome-mcp
npm root -g     # → <root>; the extension is at <root>/@mehmoodqureshi/chrome-mcp/extension-dist

Then chrome://extensions → enable Developer mode → Load unpacked → select that extension-dist/ directory. (Working from a git clone instead? Run npm install && npm run build:ext first — extension-dist/ is gitignored.)

3. Pair it: run npx chrome-mcp --print-pairing to write the handshake and print its path, open the extension's Options page, and paste the port + token from ~/.chrome-mcp/handshake.json.

Running more than one session

The extension dials exactly one bridge port, so only one chrome-mcp can drive your Chrome at a time — but every MCP host session (each Claude tab/window) spawns its own server. With a pinned --port, the newest session takes the port over: it reads the owning pid from handshake.json, confirms that process really is a chrome-mcp, and stops it. Newest tab wins; the older session's browser tools go quiet until it reconnects. Nothing that isn't a verified chrome-mcp is ever touched — a port held by some other program is reported, never killed.

Two servers can only run side by side if each has its own port and its own paired extension — i.e. a separate Chrome profile running its own copy of the extension, pointed at the other port (--port 9223). A single Chrome pairs to one server at a time, so a second server with no extension of its own can drive nothing.

One server can, however, serve several browsers at once: connections are routed by profile key (--profile <name>, matching the profile set in the extension's Options), so each paired Chrome gets its own routing slot.

Without --port, each server binds an ephemeral port (no conflict ever), but the port changes every boot — so you'd re-pair the extension each time. Pin --port plus --persist-token for a pair-once setup.

Windows

WSL2 is not required — native Windows works. One config change is, though: on Windows npx is npx.cmd, a batch shim, and MCP hosts spawn the server without a shell, which cannot execute a .cmd. So "command": "npx" fails to start. Wrap it in cmd /c:

{
  "mcpServers": {
    "chrome-mcp": {
      "command": "cmd",
      "args": ["/c", "npx", "-y", "@mehmoodqureshi/chrome-mcp",
               "--allow-domain", "example.com", "--enable-mutations",
               "--persist-token"]
    }
  }
}

Or from Claude Code: claude mcp add chrome-mcp -- cmd /c npx -y @mehmoodqureshi/chrome-mcp --allow-domain example.com

Everything else is the same — load extension-dist/ from npm root -g and pair as above.

The tools cover tabs, navigation, interaction (click/type/press/hover/ scroll/select_option), reads (get_text/get_html/screenshot/eval/wait_for), an accessibility snapshot (interactive elements with stable refs the model can target instead of guessing CSS selectors), session access (get_cookies/storage), helpers (extract_links/read_as_markdown/fill_form/download_file/upload_file), and chrome_status. upload_file sets local file(s) on a file <input> without the OS dialog (requires --enable-uploads).

click/type accept trusted: true for real OS-level input (works on React/Vue controlled inputs); interactions auto-wait for the target to appear.

Driving several tabs at once — batch

batch runs many tool calls in one request — parallel (default) or serial (with optional stopOnError). Each sub-op goes through the same policy gate, rate limit, and error handling as a direct call (no bypass, no nesting). Use it to fan work out across tabs:

// open three product pages (background, so they don't fight for focus)…
{ "name": "batch", "arguments": { "ops": [
  { "tool": "tab_new", "args": { "url": "https://a.example/p" } },
  { "tool": "tab_new", "args": { "url": "https://b.example/p" } },
  { "tool": "tab_new", "args": { "url": "https://c.example/p" } }
]}}

// …then read them all at once (wall-clock ≈ the slowest one, not the sum)
{ "name": "batch", "arguments": { "ops": [
  { "tool": "get_text", "args": { "tabId": "<a tabId>" } },
  { "tool": "get_text", "args": { "tabId": "<b tabId>" } },
  { "tool": "get_text", "args": { "tabId": "<c tabId>" } }
]}}

In parallel mode, tab-scoped ops must pass an explicit tabId — the active-tab default is unsafe under concurrency, so it's rejected rather than silently mis-routed. (tab_new, tabs_list, chrome_status are exempt.)

tab_new focuses the new tab by default (so "open X" behaves like opening a link, instead of replacing your current page — use tab_new, not navigate, to open without losing the current tab). Pass active: false to open in the background; parallel batches do this automatically.

Related MCP server: Chrome Extension MCP Bridge

Status

v0.5.0 — safe multi-tab concurrency. Adds the batch fan-out tool, makes parallel tab automation race-free (explicit-tabId guard; per-tab chrome.debugger serialization; collision-free tab_new), captures screenshots via chrome.debugger (a specific tab without stealing focus — plus true full-page and element capture), and focuses newly opened tabs by default. 111 automated tests + a gated headed extension smoke.

v0.2.0 — all six build phases complete and green. End-to-end working: npx chrome-mcp ⇄ bridge ⇄ extension ⇄ your real Chrome, with a Playwright CDP fallback. v0.2 adds the accessibility snapshot + element refs, auto-wait, cookies/storage/select_option, trusted input (chrome.debugger), a toolbar status badge, and a stable pairing token (--persist-token).

• Phase 0 — Contracts & skeleton: shared/protocol.ts (wire contract), src/executor/types.ts (Executor interface), src/security/policy.ts (default-deny policy + capability gates), src/config.ts (CLI/env/policy resolution), build + test harness.

• Phase 1 — MCP server + StubExecutor: mcp/server.ts (clean-stdout stdio), mcp/tools.ts (28-tool catalog + never-throw dispatch + drift-check), validators/envelopes/helpers, ExecutorManager + StubExecutor, cli.ts. Point an MCP host at node dist/src/cli.js today.

• Phase 2 — WebSocket bridge + auth: bridge/server.ts (loopback WS, hello-token gate, welcome/unauthorized, displacement), bridge/auth.ts (per-boot 256-bit token, atomic-0600 handshake, SHA-256 timingSafeEqual), bridge/connection.ts (id-correlation, method-aware timeouts, backpressure, reject-all-on-close, heartbeat).

• Phase 3 — ExtensionExecutor + CdpExecutor + selection: executor/extension-executor.ts (Executor over the bridge), executor/cdp-executor.ts (Playwright connect/launch + lock recovery + tab resolution), executor/select.ts (extension-if-ping-responsive else CDP). CLI now starts the bridge, writes the 0600 handshake, and serves a real backend. Adds playwright.

• Phase 4 — MV3 extension: extension/ — manifest.json, sw/ws-client.ts (dial + hello/welcome + pong), sw/executor.ts (chrome.scripting/chrome.tabs command impls), sw/router.ts (never-throw + drift), sw/background.ts (top-level listeners + 25s keepalive/reconnect), options page (manual pairing), esbuild build → extension-dist/. Verified by a live --load-extension smoke (pair → navigate → get_text). Adds esbuild + @types/chrome.

• Phase 5 — Helpers, downloads, HITL: hardened download_file (shared/download.ts — path-traversal/dangerous-ext sanitize + size cap, wired into both backends), richer read_as_markdown, and a human-in-the-loop harness (hitl/ — npm run test:hitl [-- --include-mutating]) with pure, unit-tested gating. 50 automated tests.

• Phase 6 — Packaging & docs: files whitelist (ships dist/src, dist/shared, extension-dist, LICENSE, blueprint — not source/tests), prepack build, bin, quickstart + .mcp.json snippet. Verified by a tarball install smoke (npm pack → install → MCP tools/list).

Security posture (default)

Deny-all safe mode. With no policy configured: empty domain allowlist, eval off, downloads off, mutating tools off. Opt in explicitly:

chrome-mcp --allow-domain example.com --enable-mutations
chrome-mcp --policy ./policy.json          # see policy.example.json
chrome-mcp --unsafe-all-domains            # loud footgun

The per-boot 256-bit token in ~/.chrome-mcp/handshake.json (mode 0600) is the only trust boundary; it is never written to stdout/stderr. On POSIX the mode is re-verified after every write and the server fails closed if the file ends up group/other-accessible. Windows has no such bits — chmod there only toggles the read-only attribute — so the check is skipped and the token's confidentiality rests on the per-user ACL of %USERPROFILE%\.chrome-mcp.

Develop

npm install
npm run typecheck       # server/test sources
npm run typecheck:ext   # extension sources (@types/chrome)
npm run build:ext       # bundle the extension → extension-dist/
npm test                # builds, then runs node --test on dist/test
RUN_EXT_SMOKE=1 node --test dist/test/extension-smoke.test.js   # live, headed

The extension

extension/ builds (esbuild) to extension-dist/, loaded via chrome://extensions → Load unpacked → select extension-dist/. Pair it from the extension's Options page using the port + token from ~/.chrome-mcp/handshake.json (run npx chrome-mcp --print-pairing to get the path).

Reads/interaction use chrome.scripting/chrome.tabs — no "is being debugged" banner, CSP-safe reads (isolated world), testable under Playwright. chrome.debugger is used only where it's needed and worth it: trusted: true input (real OS-level events on React/Vue inputs) and screenshot (captures a specific tab without activating it — safe under parallel batch — with true full-page and element capture). Those ops briefly show the debug banner while attached.