Browser development can be a risky place, even for a team of savvy, crowd-sourced enthusiasts. So it's no surprise that Mozilla calls their nightly Firefox build "Minefield." What is surprising is that, in general, today's version tended to be fairly stable.
The version I spent the day with, Firefox 3.7 alpha 6, offers multiple in-development improvements. Besides being built on the next version of Firefox's rendering engine Gecko, the current nightlies will eventually become Firefox 4, expected to be released later this year.
For right now, though, the nightly builds are a rough work in progress. Broad support for HTML5 is expected in Firefox 4, and support for the HTML5 audio and video codec WebM debuted just last week in version 3.7 alpha 4. For those curious to test it out, Google has posted a way to try out any WebM-enabled browser for yourself. There's also a build for 64-bit computers, a new version that Mozilla has only recently begun working on.
The nightlies also offer hardware acceleration. One way to tell if the Direct2D hardware acceleration API is working is to go here and try to resize the photos in your browser. If the change occurs smoothly, then according to a developer's blog, it's probably working.
What has made it into the nightlies, though, is the new about:add-ons. There's not much there so far, but it does represent a radical departure from the previous add-ons management window. It also marks Firefox joining the movement towards keeping browser configuration pop-up windows to a minimum, as there are new in-window sidebars for History and Bookmarks, as well. Opera and the WebKit browsers Safari and Google Chrome have been steadily moving in this direction for some time.
Other noticeable interface changes include a big orange button in the orange left corner that conceals most of the menubar options. In the current build, it's labeled "Minefield," but mock-ups for version 4 show that will change to "Firefox," most likely when the alpha builds are ready to graduate to beta status sometime in the next few months.
Folding the menubar into a single button is nothing new, showing up in Opera's refresh earlier this year most recently. Meanwhile, Chrome has done away with the menubar entirely. The debut of Google Chrome and its minimalist interface in September 2008 kicked off more than just a browser speed war; it also forced interface designers to reconsider how much of the browser needed to be visible. For Minefield users who aren't ready to abandon their menus, though, tapping the Alt key will toggle revealing the familiar format.
Minefield's interface isn't quite as minimalist as Chrome or Opera, yet. It still ships with Status bar turned on at the bottom of the browser, and it also ships with the browser titlebar intact. It does include the option to move your tabs to the top of the browser without requiring an additional extension. Speaking of extensions, most add-ons are not compatible with Minefield. For some, this is because their max version number is set lower than the current Minefield build. For others, there are serious compatibility problems that will prevent the add-on from functioning properly, or seriously decrease the stability of the browser. Add-ons such as Nightly Tester Tools and MR Tech Toolkit can force add-ons to be compatible, but you run the risk of a significantly less-stable browser.
Meanwhile, it's not clear that the out-of-process plug-in protection technology code-named "Lorentz" will debut in Firefox 3.6.4. Although it has been included in the 3.6.4 beta versions, it looks like a potential security risk is holding Mozilla back. They may wind up releasing a security fix for the hole and then retest Lorentz with the fix in place. Lorentz will be included in Firefox 4, as well.
Despite the relative stability I experienced when testing Minefield, it's definitely not something for casual users to play around with because of the ever-present potential for data loss in the browser. If you are looking to expand your comfort zone, playing around with Minefield is a relatively safe way to begin experimenting with developer's previews of upcoming software advances.