Can I see an example of a successful implementation of --user-data-dir in this MCP?

[WillCKyle]

I'm on a mac, trying to place an arg in the configuration for this MCP in cursor that will allow the browser to use my google accounts. Without that arg, the MCP initiates correctly.

I tried adding the arg "--user-data-dir /Users/[my user]/Library/Application Support/Google/Chrome/Default" but the client failed to start. I also tried:

• Placing the directory path in single quotes because "Application Support" contains a space
• Using an equals sign after --user-data-dir
• Copying this user data folder to /Users/[my user]/ChromeUserDataClone and pointing it there, with all the arg variations I tried earlier

The MCP server failed to initialize successfully for all of these attempts. This is supposed to be supported, so can someone please show me an example of this successfully implemented, on any platform or ideally on a mac?

[WillCKyle]

It's configured in my MCP.json like so:

"playwright": {
"command": "npx",
"args": [
"@playwright/mcp@latest",
[arg attempted to go here]
]
},

[pavelfeldman]

Try it without /Default?

[WillCKyle]

Nope, the client failed with each variation of that - w/wo single quotes, w/wo equals sign

Really, the question is more broad. How are these args formatted when they require a value? The only args shown in the documentation are args without a value. I'm trying --executable-path as well, still no luck.

[WillCKyle]

Update, using an = and no single quotes did successfully create the client, used with the variant of the path that didn't have a space in it. However, the user data did not get used by the tool. I would use the executable path instead, but it seems using the single quotes with a path containing a space doesn't allow the MCP client to start.

[mibrahim2001]

@WillCKyle Were you able to make it work? I want to use the Default profile. Can you share an example if you made it work successfully. Thanks!

[WillCKyle]

@mibrahim2001 I was not. What I did find working for using my logged in Chrome instance was setting up Browser Use locally using this simple guide. I think I'll install this in my projects, set it up to take commands from the agent and tell the agent to run it when needed.

[yongkangzhao]

Try it without /Default?

@pavelfeldman

can you give me a example of working mcp.json or npx command? it seems not as straight forward.

tried both of these
npx @playwright/mcp@latest --port 8931 --user-data-dir "/Users/<username>/Library/Application Support/Google/Chrome"
npx @playwright/mcp@latest --port 8931 --user-data-dir "/Users/<username>/Library/Application Support/Google/Chrome/Default"

didn't work for me. I do have two profiles in my chrome maybe that's an issue.
both version end up running without using my profile.

with the application I'm building, I see this error:

I tried removing my chrome profiles so only one is left, and the error message becomes:

[non-fatal] Tracing client error 400: {
  "error": {
    "message": "Invalid type for 'data[1].span_data.result': expected an array of strings, but got null instead.",
    "type": "invalid_request_error",
    "param": "data[1].span_data.result",
    "code": "invalid_type"
  }
}

"Invalid type for 'data[1].span_data.result': expected an array of strings, but got null instead."

somewhere the mcp server returns null.

without specifying the --user-data-dir my application works with the mcp server fine.