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Firebug – the best Firefox extension ever?

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?

2 comments:

  • # Reply from Joe Hewitt at 03:27 on 21 Dec 2006

    Hi James. Firebug is disabled by default because it adds a bit of debugging overhead which may slow down browsing, and also alerts you to errors, which some find distracting. When you’re just browsing, you probably don’t care about debugging.

    I don’t notice any slowdown on my MacBook Pro, but some people might on older computers.

  • # Reply from James at 07:50 on 21 Dec 2006

    That makes sense. I didn’t notice any slowdown myself, but then again I do use fairly fast, modern computers. The error message is also fairly discreet so it doesn’t bother me, so I’ve enabled it right across the board. I think it might be worth having a note as to the implications of enabling it though. It did make me think a bit “What am I letting myself in for?” at first.

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