If not now then when?

Firefox's new Cognitive Shield and Running Multiple Firefoxes Side by Side on OS X

Firefox has got a hot new thing they're calling "Cognitive Shield", which is a "new tab" page that shows you all your most visited sites. Google Chrome was the first browser that I'm aware of that did this, but I'm sure the Opera guys will probably jump in and say "we've had this forever". Safari's Beta 4 has one too and they're calling it "Top Sites" where they show you your most visited sites in a cover-flow style.

The design idea behind Safari's Top Sites and Firefox's Cognitive Shield could not be further apart from each other. Apple predictably went the sex appeal route with thumbnails of all the sites on a reflective black background. Contrast with Firefox's screen which appears blank until you move your mouse, then the light grey text appears, showing you the most visited sites. Use Safari Beta 4 for a few days and you'll quickly see one of it's huge drawbacks: it consumes a lot of memory trying to keep those thumbnails up-to-date. Firefox on the other hand does not consume any more memory, because it's just plain text. Safari is literally running like it has 12 (the max number of "top sites" shown) tabs open at all times, plus whatever tabs the user may have open. From a development perspective, I'm a bit perplexed as to how they would actually implement this feature in such a poor manner.

I don't want to talk a whole lot more about this, since the point of this post was to share with other people how to run different versions of Firefox side-by-side without having to worry about the beta version (3.1) overwriting profile data in your stable 3.0 version. One last thing I will say about "tab pages" is that I like them. I like this new trend to introduce tab pages to web browsers and I am especially keen on the Mozilla approach of not cluttering the screen or consuming resources keeping that screen up-to-date.

Over on the Firefox lab blog, they have detailed exactly what you need to do to try out this new feature, but it requires installing a development build of Firefox, which is undesirable if you need your browser to test functionality in other stuff you work on. Here's a couple steps to get you running multiple Firefox's at the same time, these steps are assuming you have already installed the latest stable version:

1. Launch Firefox with the profile manager, use the terminal and launch: /Applications/Firefox.app/Contents/MacOS/firefox-bin --profilemanager
2. Create a new profile (I called mine "3.1 user") and uncheck the box "Don't show at startup".
3. Exit the profile manager and go download the latest Firefox 3.1 development version.
4. When you're ready to install, instead of dropping Firefox in your Applications directory, put it somewhere else and then rename the app to something like "Firefox 3.1" or whatever makes sense for you. Optionally at this step, change the icon for this app so you will be able to tell the difference between the two versions when they are both running in your dock.
5. Now drag the app into your Applications and launch it as normal, but make sure to choose the correct profile depending on what version you are using.

If you ever remove the development version, the next time you launch Firefox just check the box "Don't show at startup" and you will no longer be bothered with the profile manager at launch. One other thing, try not to launch your different versions of Firefox and use the wrong profile. This will corrupt your profile data across versions.