what's new in Firebug 1.5?

This is a re-post from Rob Cambell’s personal weblog. Firebug 1.5 is the first release that will work with the upcoming Firefox 3.6 and also also works with Firefox 3.5. It’s currently in beta and will be available before the release of Firefox 3.6.

As of this minute, Firebug 1.5 is sitting comfortably in its third beta and available for download. This version is shaping up to be our best release yet and initial reports have been very positive regarding its stability, UI improvements and new features. So let’s take a look at some of the new features.

Improved Net Panel accuracy

One of the problems with Firebug’s Net panel in the past has been inaccurate timings. Because Firebug is entirely written in JavaScript some network and UI activity could block Firebug during long operations and cause the timings displayed there to be less than accurate. This has finally been corrected with the landing of a new service called the http-activity-distributor. For more details on the implementation and use of the newly-improved Net panel, see Honza’s blog post on the topic.

New Break Functionality

In Firebug 1.4, we introduced the concept of “break-on-next” to the Script panel. This was a “pause” button sitting between the inspect icon and the Console tab. In 1.5, we’ve extended this concept to the Console, HTML and Net panels to allow more exciting types of breaks.

break on xhr

In the Console, we’ve replaced the mini-menu Break-on-Errors option with the pause button. The reasons for this possibly contentious change was it made for a more consistent use of menus and the break button. Now, to enable Break on Errors, select the Console panel and hit the pause button. You’ll see that familiar glow to indicate that it’s waiting for an error. Now whenever an error occurs on the page, you’ll be dropped into the script panel at the line where the error occurred.

The HTML panel’s break button is a little different. This is the Break-on-Mutation feature. When this is enabled, whenever a bit of JavaScript modifies an HTML element, you’ll be taken to the Script panel and the modifying code while be highlighted. Related to this, you should be able to see modified HTML occurring in real-time in the HTML panel with affected elements and attributes being highlighted as they change in the page.

Finally in the Net panel, the break button acts as a Break-on-XHR button. This is intended to help debug AJAX apps by allowing you to halt the debugger during an XmlHttpRequest send. As in the other break types, you’ll be transported to the script panel when an XHR object fires off its request and you’ll be given the option to copy the message.

John Barton and Honza have written a great interactive demo page describing these new features on getfirebug.com.

Mixed Development

  • We made a few tweaks to the UI in this version. We replaced the “Off” label with a single “power” button (or window close button on Mac) as promised during the last release.
  • Kevin Decker added the search panel originally intended for version 1.4 with some nice options.
  • Persist option on Console and Net Panel. Save your data!
  • Improvements to the Inspector.
  • Still more to come. Between now and final release we plan on hunting down a few more bugs to make this even more stable. Feel free to download and give it a try.


  1. inerds

    awesome. cant wait to start working with my loving Firebug (1.5)! yay

    November 17th, 2009 at 11:58

  2. Corintho Fernandes

    It’s my prefer extension!! And now more powerful! o/

    November 17th, 2009 at 12:59

  3. Butteryweb

    just downloaded this beta version, so far so good!
    The search box makes everything so easy.
    Firebug really is a ‘must have’ add-on.

    November 17th, 2009 at 16:49

  4. Bruce Langston

    I feel like an alien on a different planet, browsing this this web site. Is that because I’m not a developer? I used to be. I’ve been in the business 30 years. I find I do not know what Firebug is, other than something for developers. I see no way to download it. I see a suggestion that I may find demos interesting. What demos?

    Party on…


    November 18th, 2009 at 18:35

  5. Exception e

    @Bruce Langston
    Firebug is just an add-on to firefox. Very powerfull!

    November 21st, 2009 at 03:55

  6. Cedric Dugas

    Look forward testing the new new features and have a more accurate .net panel

    November 26th, 2009 at 09:54

  7. Butteryweb

    @Bruce Langston
    Hey Bruce, check out what the fuss is all about. http://getfirebug.com/

    November 30th, 2009 at 14:52

  8. makuchaku

    Firebug rocks! Thanks for all the hard work :)

    December 21st, 2009 at 20:55

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