With an endlessly updating list of browsers being used on a variety of operating systems, web developers and designers require a tool for compatibility testing. Adobe fills this void in their suite of applications with BrowserLab, a new cross-browser compatibility tester. Released by AdobeLabs as beta in June 2009, it is still being revised through user comments and feedback. Adobe currently provides a free, limited version lasting through the end of 2010, for users to preview the application’s functionality and debugging. Starting in 2011, there will be a $10-20 monthly fee to use the service. For Dreamweaver (CS4) owners, there is a free plug-in available for download on Adobe’s website. This plug-in allows local testing of websites, while the web version requires a site to be live in order to download the code.

Currently, you can test with:

• Firefox 2.0, 3.0 and 3.5 (Windows XP and Mac OS X)
• Internet Explorer 6.X, 7.X, and 8.X (Windows XP)
• Safari 3.X and 4.X (Mac OS X)
• Chrome 3.0 (Windows XP)

Since BrowserLab’s launch last year, developers have added a number of useful features. Onion Skin Registration is one of the most useful tools within the program. It allows you to layer two separate versions (from different browsers) of your site and adjust opacity of the top layer, highlighting the differences. Rulers and Guides have also been added to the toolbox: you can pinpoint exactly where discrepancies are revealing themselves.

A feature I find particularly useful is the two-up mode. It gives you the largest available viewing room for two side-by-side browsers. You can zoom around in one window, while the other follows your movements to see the differences in similar areas.

So, what makes BrowserLab better than its competitors? This is what Adobe says:

BrowserLab offers a unique combination of speed, ease of use, and powerful diagnostic tools, with customizable testing preferences. When used with Dreamweaver CS4® software, web professionals can also test local content and different states of interactive content.

There are only a couple of reasonable competitors, each of which stack up pretty well against BrowserLab. The competitors included Litmus and (the tastelessly named) Cross Browser Testing. Both offer a very limited trial; the latter requires a credit card for access. They run significantly slower than the beta version of BrowserLab. Litmus offers features that Adobe doesn’t, including invalid HTML and CSS markups and a slightly more personalized interface.

Regardless of speculation, BrowserLab has proven itself a successful tool with useful features. Sign up for the Beta and compare it with other services for yourself while you can for free. Follow them on Twitter for updates on the project.