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debugger.html is a hackable debugger for modern times, built from the ground up using React and Redux. It is designed to be approachable, yet powerful. And it is engineered to be predictable, understandable, and testable.

Mozilla created this debugger for use in the Firefox Developer Tools. And we've purposely created this project in GitHub, using modern toolchains. We hope to not only to create a great debugger that works with the Firefox and Chrome Debugging Protocol but development community that can embed this debugger in your own projects with tools like NPM.


Circle CI status npm version PRs Welcome

Getting Setup

Here's the quick setup, if you're getting started, we recommend the detailed getting started instructions.

curl -o- -L | bash -s -- --version 0.18.1
git clone
cd debugger.html
yarn install
yarn run firefox
# create a new terminal tab
cd debugger.html
yarn start

After the debugger is setup, you can:

Getting Involved

This is an open source project and we would love your help. We have prepared a CONTRIBUTING guide to help you get started.

We strive for collaboration with mutual respect for each other. Mozilla also has a set of participation guidelines which goes into greater detail specific to Mozilla employees and contributors.


We're all on Mozilla's IRC in the #devtools-html channel on

  • Community Call Every Tuesday, Thursday at 3pm EST. Call
  • DevTools Call Every Tuesday at 12pm EST. info