Firebug

Firebug integrates with Firefox to put a wealth of development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page...

Compatibility table:

Firefox 3.6 with Firebug 1.7.3
Firefox 4.0 with Firebug 1.7.3
Firefox 5.0 with Firebug 1.8.2 (and also Firebug 1.7.3)
Firefox 6.0 with Firebug 1.8.2 (and also Firebug 1.9)
Firefox 7.0 with Firebug 1.8.2 (and also Firebug 1.9)
Firefox 8.0 with Firebug 1.8.3 (and also Firebug 1.9)
Firefox 9.0 with Firebug 1.8.4 (and also Firebug 1.9)
Firefox 10.0 with Firebug 1.9
Firefox 11.0 with Firebug 1.9
Firefox 12.0 with Firebug 1.9
Firefox 13.0 with Firebug 1.10 (and also Firebug 1.9)
Firefox 14.0 with Firebug 1.10
Firefox 15.0 with Firebug 1.10
Firefox 16.0 with Firebug 1.10
Firefox 17.0 with Firebug 1.11 (and also Firebug 1.10)
Firefox 18.0 with Firebug 1.11
Firefox 19.0 with Firebug 1.11
Firefox 20.0 with Firebug 1.11
Firefox 21.0 with Firebug 1.11
Firefox 22.0 with Firebug 1.11
Firefox 23.0 with Firebug 1.12 (and also Firebug 1.11)
Firefox 24.0 with Firebug 1.12
Firefox 25.0 with Firebug 1.12
Firefox 26.0 with Firebug 1.12
Firefox 27.0 with Firebug 1.12
Firefox 28.0 with Firebug 1.12
Firefox 29.0 with Firebug 1.12

Firebug integrates with Firefox to put a wealth of development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page.

Visit the Firebug website for documentation and screen shots: http://getfirebug.com
Ask questions on Firebug newsgroup: https://groups.google.com/forum/#!forum/firebug
Report an issue: http://code.google.com/p/fbug/issues/list

Please note that bug reports or feature requests in comments on this page won't be tracked. Use the issue tracker or Firebug newsgroup instead thanks!