Screenshot Tool Fails with "Cannot access contents of url" Error

[TargiX]

Problem Description

When attempting to use the screenshot functionality in Browser Tools MCP through Cursor tool, I consistently receive the following error:

Error taking screenshot: Cannot access contents of url "devtools://devtools/". Extension manifest must request permission to access this host.

The screenshot tool fails to access the DevTools URL, preventing me from capturing the current state of my application.
Manually taking screenshots form Devtools is working properly

Steps to Reproduce

Install the Browser Tools MCP extension
Open DevTools as SEPARATE window and attempt to take a screenshot using the MCP tool
Observe the error message about not being able to access the DevTools URL

Environment

• OS: macOS Sequoia 15.2
• Browser: Brave
• Client: Cursor
• Extension Version: 1.2.0 (same issue on previous as well)

[bmacer]

awesome @TargiX thanks for the SEPARATE window piece of info.

I was able to reproduce as well.

Asked Cursor if there was a fix, got this:

This is a known limitation with Chrome's extension security model. The issue occurs because:

1. When DevTools is in a separate window, it runs in its own window with the devtools:// protocol
2. Chrome extensions require explicit permissions in their manifest.json to access specific protocols/URLs
3. For security reasons, Chrome restricts access to certain privileged URLs like devtools://

@tedjames

[bmacer]

Probably a duplicate of #81 (or vice versa since 79 came first)

[TargiX]

@bmacer I tried to fix it with cursor, here is the PR - #85

Looks like now its working fine, I see that tool is making screenshots, but I'm not sure that its working as intended because its basically saving it to folder, then doing nothing with them.

"Allow auto paste to cursor" also doing nothing. Probably skill issue :)

Let me know that my code is makes sense in the scope of that project.

Thanks.

[bmacer]

@TargiX are you ensuring that the blinking cursor remains in the agent prompt after you submit the request for a screenshot? It is a requirement:

Alternatively, you can check your copy buffer (cmd-v somewhere that accepts screenshots). Is the screenshot copied to the buffer?

[TargiX]

@bmacer Yes, it's working now. I needed to grant permission for Wezterm, and now it's working fine. So maybe consider my PR as a potential fix for the separate devtools window.

Thanks for your help!

[DanielShterenberg]

I'm still having the same problem; The solution above didn't work for me.

Working with Cursor 0.45.

[DanielShterenberg]

Ok, I read the thread on #81.
It appears that to take a screenshot successfully, we should start the server before we start Cursor and we should close the dev-tools while taking it.

It still doesn't work most of the time.
I'm getting the following when everything is actually connected.

[TargiX]

@DanielShterenberg - you can try replace these 2 files in your extension folder, for me its working now with devtools,
don't forget to hit Update button in browser extensions section.

screenshot-fix.zip

[DanielShterenberg]

Thanks for the help @TargiX but unfortunately it didn't work me either.
I'll try to downgrade the version to the previous one and see if that helps.

BTW, the button from within the extension works.

[freely-boss]

• 你可以尝试替换扩展文件夹中的这两个文件，对我来说，它现在可以与 DevTools 一起使用，不要忘记点击浏览器扩展部分的更新按钮。

screenshot-fix.zip

@DanielShterenberg - you can try replace these 2 files in your extension folder, for me its working now with devtools, don't forget to hit Update button in browser extensions section.

screenshot-fix.zip

成功了，我替换了你给的这两个文件，在edge浏览器重新加载了插件，cursor能正常获取截图