Don't forget that the web is changing also. Sites are adding more and more crappy javascript widgets, etc... This type of stuff easily adds to memory bloat that the browser has no control over.

I almost never allow sites to run JavaScript (and even then, generally not for long). On the other hand, the growing complexity of the web has contributed to increasing the number of Firefox extensions that I use (and their size). On the third hand, Firefox leaks memory over time even with a consistent set of base windows and with JS off.

(I may be suffering from a compartment leak with my current setup, but I don't know what extension might be causing it and trying to find out is going to be a pain.)

For me, Firefox became completely unusable in the stretch from 3.0 to 4.x – to the point of second-long pauses on every click, and occasional minute-long ones. 100% CPU was par for the course. I was forced to switch to Chrome, which cuts against my grain in every way. I have written rants about its bookmark management, and its extensions have always felt like foreign bodies in the browser, limited in power and with janky UIs. But I had no other choice. Those days were dark with frustration.

Then Firefox 5.0 made a dramatic leap in responsiveness that made me leap with hope. But ultimately I stayed on Chrome. Firefox was usable again, but only for a short while before it required a restart to slough off the quickly accumulating lag. Chrome at that time also ran circles around Firefox on JS-heavy sites like the current incarnation of Flickr.

But Firefox got better with each version. Once FF8 rolled around, I gleefully ditched Chrome, never to return to it. The issues I’ve had with it from the start have never improved. (It continues to lead a lonely existence on my machines just so I wouldn’t have to install Flash in Firefox. That’s all it’s for any more to me, it’s a wrapper around Flash.)

With each version since 5.0, Firefox has gotten better, and then better again – CPU load and memory consumption both have gone way down. And the news out of the Memshrink and Snappy teams sound great (e.g. Firefox 15 will ship with a mechanism to drastically cut down on leaks caused by extensions). It is a ways from perfect still, but it is well sufferable today.

I await now the day when an idle Firefox instance with 100 tabs open runs up no more CPU load than one with 5 tabs one. Nowadays it really looks as if we’ll get there, some time though it may yet take. The competition from Chrome has done Firefox a world of good.

So there you have my experience with the browser. From my perspective I’d say: just wait a while and see.

—Aristotle Pagaltzis

I have to agree with Aristotle; the version in squeeze was a lot slower than in lenny, and rapid release was pretty bad. But they've improved the upgrade process a lot (auto-marking extensions as good), and Firefox 14 is decidedly snappy.

Frankly Chrome (not that I've used it seriously in a while) sucks a lot of RAM too; whether that is worse than Firefox's appetite for CPU is open to argument.

Chrome is in fact very memory-hungry. It is blazing fast but you pay for that with lots of RAM for each tab (actually process, to be precise – it does not spawn another process for every tab). Up to a dozen it is reasonable, and another dozen are OK, but it is not suited to someone who routinely has 50 or 80 tabs open. And once you really pile on the tabs beyond that, the UI gets into serious trouble even keeping up with user input, until eventually it becomes entirely incommunicado – even though the pure rendering inside individual tabs remains snappy (once the OS has finished paging in their data, that is…). You can viscerally sense the multiprocess model within.

—Aristotle Pagaltzis