The most popular web development tool for Firefox
* Inspect HTML and modify style and layout in real-time
* Accurately analyze network usage and performance
* Extend Firebug and add features to make Firebug even more powerful
* Get the information you need to get it done with Firebug.
# Just the way you like it
Firebug is always just a keystroke away, but it never gets in your way. You can open Firebug in a separate window, or as a bar at the bottom of your browser. Firebug also gives you fine-grained control over which websites you want to enable it for.
# Inspect and edit HTML
Firebug makes it simple to find HTML elements buried deep in the page. Once you've found what you're looking for, Firebug gives you a wealth of information, and lets you edit the HTML live.
# Tweak CSS to perfection
Firebug's CSS tabs tell you everything you need to know about the styles in your web pages, and if you don't like what it's telling you, you can make changes and see them take effect instantly.
# Visualize CSS metrics
When your CSS boxes aren't lining up correctly it can be difficult to understand why. Let Firebug be your
# Only show applied styles in Style side panel (issue 223). If you dealing with a page that uses a lot of CSS rules and the Style side panel looks messy showing also overwritten declarations, you can utilize a new Only Show Applied Styles filter.
# Goto a line number available in the Script panel is now more visible in the UI
# Now you can pass even a line number when invoking an editor. This way you can start script editing immediately at the right place and avoid tedious scrolling (issue 1480).
# Better representation of the Date object within Firebug console (issue 4088). If you log a date object into the console you can see its actual value now.
# Firebug console also supports logging of the globalStorage field
# Extending Firebug: better API for reusing an info-tip within a Firebug extension (issue 4175).