Firebug

Gave every browser the F12 key, then merged into them

Replaced
19902026

Firebug was the Firefox extension that invented modern web development tooling: inspect an element, edit its CSS live, watch network requests, step through JavaScript. In January 2006 it introduced the F12 shortcut that now opens developer tools in every browser on earth. It was retired in 2017, after its team and its ideas were absorbed into Firefox itself.

Timeline [edit]

  1. 2006
  2. January 2006 Launch
    Joe Hewitt writes Firebug

    A debugging panel inside the browser, where before there was alert().

  3. 31 January 2006 Feature
    F12 opens the tools

    Introduced in 0.2.3. Every browser copies it.

  4. 2014
  5. 2014 Version
    Firebug 2.0

    Syntax highlighting, pretty printing and a DOM event inspector.

  6. 2016
  7. December 2016 Shutdown announced
    Firebug merges into Firefox DevTools

    Its developers join the Mozilla team rather than rebuild beside it.

  8. 2017
  9. 14 November 2017 Shutdown
    Firefox 57 removes XUL add-ons

    Firebug stops working.

The site through time

Browse getfirebug.com as it was, via the Internet Archive's Wayback Machine:

2006 2008 2010 2012 2014 2016 2017 Full archive →

Ownership [edit]

Joe Hewitt 2006–2007 Founded Wrote the first version; one of the original Firefox creators
Firebug Working Group 2007–2017 Spin-off Open source group that maintained it until the merge into Firefox DevTools

Why it shut down [edit]

Official line: Firefox 57, released on 14 November 2017, removed support for XUL add-ons, which ended Firebug. Its functionality had already been merged into the built-in Firefox DevTools, and several of its core developers had joined that team.

Our analysis: Firebug did not lose to a competitor. It was made impossible by the architecture change that Firefox needed to survive: multiprocess Firefox would have required an extremely costly rewrite, so the Firebug working group chose to merge the tool into the browser instead of rebuilding it beside it.

History [edit]

Before it, you used alert()

Joe Hewitt, one of the original Firefox creators, wrote Firebug in January 2006. Before it existed, debugging a web page meant reading source, adding alert() calls, and guessing why a layout was wrong.

Firebug gave you a panel inside the browser. You could point at any element and see its HTML, edit its CSS and watch the page change under your hands, inspect the live DOM, follow every network request with its timing, and set breakpoints in JavaScript. Everything a developer does with the browser today, essentially in the form it is still done.

Its 0.2.3 release on 31 January 2006 introduced a small convention: F12 opened the panel. That shortcut is now in Chrome, Edge, Safari and Firefox, and almost nobody knows where it came from.

It was BSD licensed and later maintained by the Firebug Working Group rather than one person. It was also used well beyond front-end work, in security testing and performance analysis, and Firebug Lite carried a version of it to browsers that were not Firefox.

Made impossible

Firefox needed to become multiprocess to stay competitive on stability and security, in a project called Electrolysis. Firebug was not designed for that world, and making it work would have meant an extremely difficult rewrite that its volunteers did not have the resources for.

So they made a better decision than most projects in that position would. Rather than compete with the browser's own tools, they folded into them. Firebug.next was built on top of Firefox DevTools, and core Firebug developers, among them Jan Odvarko and Mike Ratcliffe, joined the DevTools team. Mozilla published a post in December 2016 titled "Firebug lives on in Firefox DevTools", which was accurate rather than consoling.

The last version

Firefox 57, Quantum, shipped on 14 November 2017 without support for the old XUL extension format, and Firebug stopped working. Mozilla published "Saying goodbye to Firebug" the month before.

Its authors are in the tools you use now, and so is its keyboard shortcut.

Similar projects

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Sources [edit]

  1. Saying Goodbye to Firebug Mozilla Hacks 1 October 2017 [archived]
  2. Firebug lives on in Firefox DevTools Mozilla Hacks 1 December 2016 [archived]

Last verified: 13 August 2026. Spotted an error? Suggest an edit (corrections with sources are reviewed and applied).