Hacktoberfest 2026: the issues maintainers tagged for October, open and beginner-friendly. Browse Hacktoberfest issues

"Couldn't find the Firefox executable" when launching in attach mode

Open
#282 1 comment 1 reaction 0 assignees View on GitHub

Nobody has claimed this yet.

Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
45/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
typescript, vscode

Research direction

Start with the attach-mode instructions in the README and reproduce the configuration using a globally incorrect firefox.executable setting. Trace how the attach launch reads that setting and produces the error; done means attach mode no longer requires an unused executable, or the message clearly identifies the global extension setting.

Written by the indexing model from the issue text.

Description

I am getting the Couldn't find the Firefox executable when launching in attach mode. I am asking myself now if this is a wanted behaviour, since I wouldn't expect that the executable is needed for that.

Background

I was following the instructions for launching in attach mode in the README.
Accordingly, I have set up a launch.json that contained the recommended block:

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Attach to localhost",
            "type": "firefox",
            "request": "attach",
            "url": "http://127.0.0.1/"
        }
    ]
}

My firefox had the necessary about:config changes and launched fine in debug mode with

"C:\Program Files\Mozilla Firefox\firefox.exe" -start-debugger-server

When I launched the debug session in vscode with this configuration I got the Couldn't find the Firefox executable error.

Cause

The firefox.executable config was set globally to a wrong location.

Two things that I think would have improved my situation

  • the error message would point out that this is set in the global extension settings
  • the error would not be thrown since (correct me if I am wrong) the executable is not called at all in attach mode
Dominant language
TypeScript
Stars
447
Forks
76
PR merge metrics
No merged PRs in 30d

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from firefox-devtools/vscode-firefox-debug

All issues in firefox-devtools/vscode-firefox-debug

Similar issues

More TypeScript issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.