whatisgithub

What is debugger?

firefox-devtools/debugger — explained in plain English

Analysis updated 2026-06-26

4,603Audience · developerComplexity · 1/5Setup · easy

In one sentence

The archived home of the Firefox JavaScript debugger, which lets developers pause and step through webpage code, active development has moved to Mozilla's central repository and contributions no longer happen here.

Mindmap

mindmap
  root((firefox debugger))
    What it is
      Archived repo
      Historical reference
    Current Home
      Mozilla central repo
      Bugzilla tracker
    How to Contribute
      Codetribute issues
      Matrix chat room
    History
      300 plus contributors
      Thousands of commits
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Code map

Detail Auto

An interactive map of this repo's files and how they connect — its source is parsed live in your browser. Click Visualize to build it.

filefunction / class

What do people build with it?

USE CASE 1

Find links to Mozilla's current debugger contribution guide and beginner-friendly issues on Codetribute.

USE CASE 2

Read the history of the early open-source Firefox debugger development done in the open on GitHub.

USE CASE 3

Follow the Matrix chat room link to ask questions about contributing to the Firefox debugger today.

How does it compare?

firefox-devtools/debuggerbespokesynth/bespokesynthbingyanstudio/lapiscv
Stars4,6034,6034,603
LanguageC++CSS
Setup difficultyeasyeasyeasy
Complexity1/53/51/5
Audiencedevelopergeneralgeneral

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · easy Time to first run · 5min

This repository is archived, actual development and issue tracking happen in Mozilla's central repository.

So what is it?

This repository was the home of the Firefox JavaScript debugger during the first three years of its development. The debugger is the tool built into Firefox that lets web developers pause their code, step through it line by line, and inspect what is happening inside a running webpage or application. Development has since moved to Mozilla's central code repository, which is where all active Firefox browser code lives. This GitHub repository is no longer where contributions are made or issues are tracked. The README points contributors to Mozilla's own documentation site, their bug tracker at Bugzilla, and a Matrix chat room for questions. The repository was notable for being an early experiment in developing a major browser component in the open on GitHub rather than inside Mozilla's internal infrastructure. During that period, more than 300 volunteers contributed thousands of commits and helped build features that are still part of the Firefox debugger today. For anyone interested in contributing to the Firefox debugger now, the README links to a contribution guide and a list of beginner-friendly issues on Mozilla's Codetribute platform. The actual code is no longer here. This is a historical repository. If you are looking for the current debugger source code or want to file a bug, the README's links will take you to the right places.

Copy-paste prompts

Prompt 1
Where can I find beginner-friendly issues to start contributing to the Firefox JavaScript debugger?
Prompt 2
What is the current process for contributing to the Firefox devtools debugger on Mozilla's central repository?
Prompt 3
How do I set up the Firefox debugger development environment for contributing to Mozilla?
Prompt 4
What features were built during the open GitHub development phase of the Firefox debugger?

Frequently asked questions

What is debugger?

The archived home of the Firefox JavaScript debugger, which lets developers pause and step through webpage code, active development has moved to Mozilla's central repository and contributions no longer happen here.

How hard is debugger to set up?

Setup difficulty is rated easy, with roughly 5min to a first successful run.

Who is debugger for?

Mainly developer.

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