Firebug Group Releases 1.2

John Resig, a member of Mozilla's Firebug development team, announced yesterday that the final version of Firebug 1.2 had been released. Firebug is a debugger for HTML, CSS, and JavaScript that sits within the Firefox Web browser. It has become an essential tool for Web developers, particularly those who use the modern technique known as "Ajax" ("asynchronous JavaScript and XML").

Firebug is popular because it solves the long-standing problem of debugging Web pages. Before Firebug, the two main methods for debugging Web applications were the server's error log (to which all error-related data was sent) and the HTML source code (making the debugging output visible to all users via the "view source" function). But with JavaScript becoming an increasingly important player in the creation of dynamic Web sites, and with CSS (cascading stylesheets) determining the formatting, the combination of error logs and "view source" was getting painfully difficult.

This latest release of Firebug has been a long time coming, with beta versions stretching back many months. As Resig notes in his blog announcement, users who had not been working with the beta version of 1.2 might be surprised to find that they are being asked which portions of Firebug should be activated. The reason is that activating Firebug has the effect of slowing down Firebug across the board, by what Resig estimates to be 25 percent.

Firebug has become the de facto standard for Web debugging, both because it does so much, and because it does it well. Experimenting with CSS changes no longer requires that you reload a page dozens of times; using Firebug, you can dynamically edit an HTML element's styling, looking at the effects as you change each variable value. Similarly, Firebug's JavaScript console makes it easy to work with JavaScript interactively. Firefox always included a JavaScript console, and it was always possible to enter code in real time. Firebug takes this to a whole new level, displaying JavaScript objects in an easy-to-read form, and even highlighting DOM elements referenced in the debugger.

Firebug also provides debugging and profiling support for behind-the-scenes Ajax calls, making it possible for a developer to see what HTTP request was sent to the server, including parameters, and what response was received -- along with an indication of when the call was made, and how long it took to execute.

In the last year, we have seen Firebug turn into a platform with its own plugins. The best-known plugin is almost certainly YSlow, developed by Yahoo's engineering team in order to better understand the source of application bottlenecks.