Firefox 3 is well into its beta process. I’ve been using it for some time now, and it’s stable and fast. There are also lots of visual improvements that make it easier to see things like download status and bookmarks.

But much of the work is happening under the covers. Browsers are the new OS, runnning all sorts of internal applications. Whether they’re plug-ins or full-blown video games built in Flash, it’s not uncommon for my browser to be the biggest consumer of memory on my desktop. Yep, more than Word. More than Outlook.

As users demand richer and richer client-side experiences, something most web operators take for granted — the browser — is once again a thing to worry about. I’ve played with Blist and Liquidplanner, and both are pretty much full desktop apps that stretch my PC pretty hard.

The good news is the folks at Mozilla have been hard at work on memory consumption. Here’s a comparison across leading browsers.

Reading memory graphs, you can learn four things:

• If they’re horizontal, the application doesn’t “leak” memory. That means that over time, it doesn’t lose track of memory it’s claimed for itself, which ultimately consumes all the memory in the system. If they have a consistent angle over time, that means they leak memory.
• If they are spiky, they are constantly allocating and cleaning up memory (which is known as “garbage collection”) whereas if they’re less so, they don’t spend as much time cleaning up after themselves.
• If they don’t make it all the way to the end (which is the case for Safari) they crashed.
• The height of the graph line is, of course, how much memory they consumed to do the same thing.

The Firefox team should be proud of what they’ve accomplished in this graph; they’ve also made the browser faster in the process. What’s interesting about Open Source projects is that the “cool” ones with a following get their pick of brilliant developers. It’s like natural selection for coders. And Firefox is clearly winning the browser evolution game right now.

(It should also be noted that lots of PC-browser people have a hate-on for Apple right now, since the latest version of iTunes includes the Safari browser as a default update. There’s a great discussion of the security consequences of this. Folks berate Microsoft for using Windows dominance to get people using Internet Explorer. By bundling Safari as part of an iTunes patch, Apple is doing a similar thing.)