Firebug - the best Firefox extension ever?

This post is more than 17 years old.

Posted at 21:40 on 20 December 2006

I came across Firebug this morning via Matt Mullenweg's blog. It is without a doubt one Firefox extension that no web developer should do without.

It's an awesome plugin. You can debug and profile your Javascript code, step through it line by line, set breakpoints, inspect objects and variables, and quickly find errors when they happen, with detailed and useful information. It has a command line that lets you execute Javascript on the fly. You can edit your HTML and CSS on the fly and have the changes show up immediately, explore the DOM, and monitor the network activity involved in each page request, showing you the HTTP request and response headers for each file that it fetches.

All in all, it has just about everything you need to develop client-side JavaScript effectively and easily. And best of all: like Firefox itself, it's free and open source.

Just one thing I don't understand though. Once it is installed, it is disabled by default and you have to enable it, either globally or on a site-by-site basis, before you can use it. I presume that there's some rationale to this -- possibly something to do with either security, performance or stability -- but I'm not sure what it is. Can anyone enlighten me?