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Advanced usage

Concurrent sessions

Most MCP clients start one Chrome DevTools MCP server per conversation. If your client shares a single server instance across concurrent agents or subagents, start the server with --experimentalPageIdRouting. This exposes pageId on page-scoped tools so each agent can route tool calls to the tab it is working with.

{
  "mcpServers": {
    "chrome-devtools": {
      "command": "npx",
      "args": [
        "-y",
        "chrome-devtools-mcp@latest",
        "--experimentalPageIdRouting"
      ]
    }
  }
}

If you run multiple independent MCP client sessions and want each session to launch its own temporary Chrome profile, also pass --isolated. This avoids sharing the default Chrome DevTools MCP user data directory between those server instances.

User data directory

By default, chrome-devtools-mcp starts a Chrome's stable channel instance using the following user data directory:

  • Linux / macOS: $HOME/.cache/chrome-devtools-mcp/chrome-profile
  • Windows: %USERPROFILE%\.cache\chrome-devtools-mcp\chrome-profile

For non-stable channels, the channel name is appended to the directory name, for example chrome-profile-canary.

The user data directory is not cleared between runs and is reused for subsequent runs with the same channel. Only one browser can use it at a time. Set the isolated option to true to use a temporary user data directory instead which will be cleared automatically after the browser is closed.

Connecting to a running Chrome instance

By default, the Chrome DevTools MCP server will start a new Chrome instance with a dedicated profile. This might not be ideal in all situations:

  • If you would like to maintain the same application state when alternating between manual site testing and agent-driven testing.
  • When the MCP needs to sign into a website. Some accounts may prevent sign-in when the browser is controlled via WebDriver (the default launch mechanism for the Chrome DevTools MCP server).
  • If you're running your LLM inside a sandboxed environment, but you would like to connect to a Chrome instance that runs outside the sandbox.

In these cases, start Chrome first and let the Chrome DevTools MCP server connect to it. There are two ways to do so:

  • Automatic connection (available in Chrome 144): best for sharing state between manual and agent-driven testing.
  • Manual connection via remote debugging port: best when running inside a sandboxed environment.

Automatically connecting to a running Chrome instance

Step 1: Set up remote debugging in Chrome

In Chrome (>= M144), do the following to set up remote debugging:

  1. Navigate to chrome://inspect/#remote-debugging to enable remote debugging.
  2. Follow the dialog UI to allow or disallow incoming debugging connections.

Step 2: Configure Chrome DevTools MCP server to automatically connect to a running Chrome Instance

To connect the chrome-devtools-mcp server to the running Chrome instance, use --autoConnect command line argument for the MCP server.

The following code snippet is an example configuration for gemini-cli:

{
  "mcpServers": {
    "chrome-devtools": {
      "command": "npx",
      "args": ["chrome-devtools-mcp@latest", "--autoConnect"]
    }
  }
}

Step 3: Test your setup

Make sure your browser is running. Open gemini-cli and run the following prompt:

Check the performance of https://developers.chrome.com

Note

The autoConnect option requires the user to start Chrome. If the user has multiple active profiles, the MCP server will connect to the default profile (as determined by Chrome). The MCP server has access to all open windows for the selected profile.

The Chrome DevTools MCP server will try to connect to your running Chrome instance. It shows a dialog asking for user permission.

Clicking Allow results in the Chrome DevTools MCP server opening developers.chrome.com and taking a performance trace.

Manual connection using port forwarding

You can connect to a running Chrome instance by using the --browser-url option. This is useful if you are running the MCP server in a sandboxed environment that does not allow starting a new Chrome instance.

Here is a step-by-step guide on how to connect to a running Chrome instance:

Step 1: Configure the MCP client

Add the --browser-url option to your MCP client configuration. The value of this option should be the URL of the running Chrome instance. http://127.0.0.1:9222 is a common default.

{
  "mcpServers": {
    "chrome-devtools": {
      "command": "npx",
      "args": [
        "chrome-devtools-mcp@latest",
        "--browser-url=http://127.0.0.1:9222"
      ]
    }
  }
}

Step 2: Start the Chrome browser

Warning

Enabling the remote debugging port opens up a debugging port on the running browser instance. Any application on your machine can connect to this port and control the browser. Make sure that you are not browsing any sensitive websites while the debugging port is open.

Start the Chrome browser with the remote debugging port enabled. Make sure to close any running Chrome instances before starting a new one with the debugging port enabled. The port number you choose must be the same as the one you specified in the --browser-url option in your MCP client configuration.

For security reasons, Chrome requires you to use a non-default user data directory when enabling the remote debugging port. You can specify a custom directory using the --user-data-dir flag. This ensures that your regular browsing profile and data are not exposed to the debugging session.

macOS

/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --remote-debugging-port=9222 --user-data-dir=/tmp/chrome-profile-stable

Linux

/usr/bin/google-chrome --remote-debugging-port=9222 --user-data-dir=/tmp/chrome-profile-stable

Windows

"C:\Program Files\Google\Chrome\Application\chrome.exe" --remote-debugging-port=9222 --user-data-dir="%TEMP%\chrome-profile-stable"

Step 3: Test your setup

After configuring the MCP client and starting the Chrome browser, you can test your setup by running a simple prompt in your MCP client:

Check the performance of https://developers.chrome.com

Your MCP client should connect to the running Chrome instance and receive a performance report.

If you hit VM-to-host port forwarding issues, see the “Remote debugging between virtual machine (VM) and host fails” section in troubleshooting.md.

For more details on remote debugging, see the Chrome DevTools documentation.

Debugging Chrome on Android

Please consult these instructions.