Web developers need no longer deal with the flakiness of Venkman, Mozilla’s venerable but stagnant JavaScript debugger.

With the release of FireBug 0.4, an excellent extension for analyzing JavaScript and CSS errors and XMLHttpRequest operations (AJAX) that we have covered before, Firefox now has a powerful, up-to-date debugger that you don’t need to hack to get working.

Firebug Debugger screenshot

In addition to standard debugging capabilities like setting breakpoints, stepping through code, and inspecting variables, FireBug adds support for checking assertions, automatic breaking on JavaScript errors, and more.

If you do any JavaScript work at all, grab FireBug now and consider making a donation to developer Joe Hewitt, who built the thing in his spare time.

Kevin began developing for the Web in 1995 and is a highly respected technical author. Kev is a world-renowned author, speaker and JavaScript expert. He has a passion for making web technology easy to understand by anyone. Yes, even you!

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  • http://webtech.lv kaklz


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  • http://www.ionbee.net Ilija Studen

    One of the best FF extensions ever. I’ll need to reinstall it because Debugger tab is not visible after the upgrade… Or I missed something?

  • Qani

    You have to have Firefox 1.5 installed, anyways thanks for the heads up, I will definetly be using this in the near future!

  • http://www.ionbee.net Ilija Studen

    Simple reinstallation fixed the problem. So, if you upgrade FireBug and don’t have debugger tab visible just reinstall.

  • http://www.dustindiaz.com polvero

    With the latest JS Debugger in Firebug, I’ll have to go back and reinstall it. Otherwise it was just another validator that that alerted me of the hundreds of invalid webpages I visit everyday.

    Just briefly after looking at some of the latest screenshots I like how you can view logs of xmlHttpRequests and their responses. I think I’m really going to like this tool now :)

  • http://www.digitalamit.com/ Amit

    Cool. So I can now start fixing those bugs now :)

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  • donaldduck

    It’s a nice debugger, but venkman is more powerfull. By the way: I had never Problems with venkman.

  • Ghandi

    When I have ‘Show XMLHttpRequests’ marked, it “steals” the request that I make. Which makes it kind of a pain to use for debugging requests.

    Anyone else have that problem? or do I not implement something right?

    That would be my only problem, otherwise it is great.

  • boriscy

    This is a great debugger, be cautioned to put break on errors when you are working with XMLHttpRequest

  • Anonymous

    Does anyone know if there is an extension that can debug php like this?
    If not, what php debuggers are good? I’m goint to take a look at NuShpere PhpED soon.

  • Ghandi
  • Akela

    Nice Javascript debuggers review can be find here:

  • Sam

    from where can i download firebug can u plz give the details of the URL for the firebug ?

  • http://www.sitepoint.com AlexW
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