The Complete Field Guide to Testing Firefox 3

The Complete Field Guide to Testing Firefox 3

If you’re sick of Firefox 2 eating up over a gigabyte of memory only to freeze up and crash, it may be time to move onto Firefox 3. The new version of our favourite browser has seen its fifth and final beta release, and Mozilla says its for testing purposes only. However, the Firefox 3 beta is leaner, meaner, faster, and just plain better than Firefox 2—and don’t tell Daddy Mozilla, but even at this early stage, we’ve found it to be stable enough for full-time use. There are a few ways you can start using Firefox 3 without blowing your browser setup to hell or losing your most important extensions. Here’s how.

Why Firefox 3 Now

Firefox 3 is in a late-stage beta, which means bugs are still getting reported and features are still getting finalised. Its next iteration will be a feature-complete release candidate, with the final public release due out in June. You can play it safe and wait till June, of course. However, Firefox 3 is chock full of new features that are reason enough to test-drive it—like a smarter address bar, better bookmarks, more native look for Mac, Windows, and Linux.

But the most compelling reason not only to try it out but to switch to Firefox 3 for regular browsing now? Significantly improved memory management and much-reduced risk of crashes. Firefox 3 just doesn’t hog all your RAM, seize your computer, and flip out with the spectacular regularity of Firefox 2. Plus it’s just plain faster dealing with the web pages it opens while it’s not crashing. If that’s enough to convince you, read on for how to get into the beta without hosing your beloved browser setup.

Windows: Play It Safe with Self-Contained Portable Firefox 3

portablefirefox.png If you want to use Firefox 3 without losing Firefox 2 or touching its settings, you want the portable Firefox 3 beta application. This standalone, self-contained version of Firefox isn’t just for thumb drives. Save it to any folder on your computer (I prefer one called Firefox 3b5 on my desktop) and it creates a whole new user profile and runs completely separate from Firefox 2. One catch: you can’t run Firefox 2 and portable Firefox 3 at the same time.

Download the portable Firefox 3 Beta 5 for Windows

When you run Firefox 3 portable you’ll start out with a fresh profile that doesn’t have your extensions, bookmarks, and homepage set. Instead of going through all the work of setting those up again, you can copy your Firefox 2 user settings to Firefox 3 portable. Here’s how.

  1. First, make sure NO versions of Firefox are running at all, but that you’ve run Firefox 3 portable at least once.
  2. Navigate to the Firefox 2 profile folder you want to copy to Firefox 3. (Here’s where to find it; most likely it will have the word “default” in the folder name.)
  3. Copy that entire folder and paste it into the Your-Firefox3-Folder/Data/ folder.
  4. Rename the existing profile folder in Your-Firefox3-Folder/Data/ to something else (like profile.bak).
  5. Finally, rename the profile folder that you just copied (something like nsm1chqs.default) to profile.

Now, launch Firefox 3 portable, and you should see all your Firefox 2 customisations there.

If you’ve never worked with Firefox user profiles before, see this article for more on how to find, create, and edit them.

Mac: Get Firefox 3 Using a Fresh User Profile Without Replacing Firefox 2

Mac users can download and install Firefox 3 without replacing Firefox 2, too. Just download the beta, but don’t copy it into your Applications folder as usual. Instead, save the Firefox 3 beta somewhere other than Applications, and rename it something other than Firefox (like Firefox_3_Beta).

Then, to make sure Firefox 3 isn’t manipulating and editing your Firefox 2 profile, create a new one for exclusive Firefox 3 use. Here’s more on how to do that from Tech Recipes.

Go Whole Hog (With a Backup)

mozbackup.png If you’re feeling really courageous, you can just wipe out Firefox 2 entirely and dive into Firefox 3 full-time, like I did. This means Firefox 3 will take over your existing Firefox profile. While I haven’t seen problems with this on Windows or Mac, backups are always good insurance. So just to be safe: back up your Firefox profile, just in case you need to revert to Firefox 2 at some point in the future. (Note: MozBackup is for Windows only. Mac users can back up their profile manually by making a copy of their user profile folder.)

Update: Several commenters point out that the FEBE Firefox extension also backs up your browser profile, and works across platforms. Thanks all!

Then, download the Firefox 3 beta and install as usual.

Make Your Extensions Work with the Firefox 3 Beta

Now that you’re running Firefox 3 the first thing it’ll tell you is that your extensions aren’t compatible with the new version. Don’t panic. It’s true that many Firefox extension developers haven’t updated their add-ons to work with Firefox 3. But in many instances, this is just a matter of the extension reporting back to the application that it isn’t yet compatible, even though the add-on might work anyway. Instead of waiting for your favourite extensions to get updated, you can tell Firefox to enable them no matter what.

There are two ways to do this:

  • Download the Nightly Tester Tools extension. Once it’s installed and you’ve restarted, your Firefox 3 Add-ons dialog will have a “Make all compatible” button, as pictured. Press that puppy to make your extensions work with Firefox 3 (after a restart, that is). nightlytestertools.png
    Note that you may still get a message about extensions that don’t “provide secure updates” even after hitting this button. Use about:config as detailed below for a workaround to the secure updates issue.
  • Manually edit Firefox 3’s configuration to run extensions no matter what. Here’s how to edit about:config values to get Firefox 3 to use your favourite extensions.

Are you a Firefox 3 convert? What’s your testing experience been like? Let us know in the comments.

Gina Trapani, the editor of Lifehacker, is in love with Firefox 3 even in its fetal stage. Her weekly feature, Geek to Live, appears every Tuesday on Lifehacker AU.


  • Hi Gina. I can’t tell you how glad I am that I stumbled across this article. I’ve been limping along with a corrupted (can’t edit application associations) installation of Firefox 1.5 because of absolute disasters I’ve had in the past trying to upgrade FF and still retain functionality of the previous release. When I saw how many of my extensions were incompatible with the new version, that sealed it for me. It was still better to keep the outdated corrupted version.

    You have enlightened me to the fact that there is a portable version that does not require you to trash your existing installation. As if that were not revelation enough, you also show how you can copy over your profile AND force compatibility with old extensions that are no longer available for current versions! I tried the 3.0 beta but couldn’t reuse the session manager from TabMix Plus. So I installed FirefoxPortable 2.0 and using your methods have nearly full use of all my old extensions including the Session Manager. Wow! And the portable is so much faster loading and reloads pages much faster when I go back to a previous page. This is a real godsend.

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