Same Here! I typically have 10+ tabs open so I thought 4 would be great with grouping. After about 2 hours+ I have to Kill Firefox and restart it due to the browser dragging. I do use Firebug & Colorzilla. Now I have to open a Chrome or IE9 (which is pretty quick now..sigh) session to grab info if I'm in the middle of a Wordpress update using Firefox just to finish a project. Then I'm back to Killing Firefox and restarting. Help - Where's the "go back" button - 3.x didn't have this problem!

Yes I have the same problems with FF 4 many tabs and some extansion like FireBug, Webdeveloper Tool.. memory usage 1GB-2.5GB.

Hehe I hit 2GB, just yesterday. I admit I had open around 10 Tabs and had some videos loading but then it started lagging. I opened up ProcessExplorer then WTF. Serious Memory Leak Issues. 2GB+ Comsumed by Firefox.exe only. :( I feel sad that I had to temporaryly switch to chrome/IE to get my work done.

I'm having to restart Firefox every half an hour or so :( Facebook especially seems to exacerbate the problem, has anyone else noticed this?

I had a bad leak with FF 3.6.x on Windows Vista Home Premium - would grow to 1G in little more than 24 hours and with fewer than 10 tabs. I never tried to disable all add-ons and extensions. Now here I am with FF 4.0, and the leak is just as bad, even after I disabled or removed everything except Google Toolbar for Firefox 7.1.20101113Wb1 and Microsoft .NET Framework Assistant 0.0.0. Over 1G in 24 hours. Just now I restarted in Safe Mode, I'll see how that goes.

FF 4.0 running in safe mode quickly reached 300M with about 6 tabs open. In the four hours since then, I have opened a few more tabs and watched the memory bounce around from about 220M to 300M, but it seems to mostly stay at the high end. Based on my previous post, I would say that safe mode solves the memory leak - and since the only running extensions previously were Google Toolbar and .NET Framework Assistant (don't even know what it's for), it should be pretty simple to find the culprit now!

SafeMode disables more than just installed extensions, but I haven't been able to find an exact listing of exactly what else is disabled. My guess is that the plugin-container process might be disabled, too - but I haven't tested that hypothesis as I don't seem to be having a problem with a memory leak in either Firefox 3.6.16 or Firefox 4.0.

I have this same problem. It's VERY annoying. I can always tell when I've had FF open for too long because the fan on my Mac starts going because the SSD has gotten so hot. I'm running 10.6.7.

I currently have eight tabs open. FF is using 12.1% of my CPU (and climbing) and 300MB of RAM (and climbing). However, it is using 3.21 GIGABYTES of virtual memory.

This is atrocious. I can't keep the program open for any real length of time or the system overheats significantly. As this is a brand-new Mac with 8GB of RAM and quad-core i7 and 256GB SSD, it shouldn't be brought to its knees by Firefox, of all things.

(It should be noted that I had similar problems with my previous Mac (2008) and Firefox 4.)

I now have seven tabs open (having closed three) and FF is now using between 13 and 20% CPU, as well as 475MB RAM and 3.35 GIGABYTES of virtual memory.

Firefox 4.0 On Mac OS X with 10 tabs open it takes about 500MB (Observed in Activity Monitor). After closing all windows and tabs of Firefox, not a single MB of memory is released, which is quite ridiculous (unlike on Windows, closing all windows and tabs of Firefox on Mac OS X will not shut it down unless you select "Quit Firefox" from the menu). I would imagine with no windows open, Firefox should occupy only a few MBs of memory for basic background tasks, which is obviously not the case.

I'm running Win 7 64bit on an i5 Intel with 4Gb RAM.

I can't claim any records, Firefox 4 managed to freeze up by hogging a mere 1.6GB of RAM. I have uninstalled 3.6.16 three times and tried FFX 4 in Safe Mode, without add-ons and with add-ons. Each time it seizes up after about an hour - Task Manager shows huge memory usage.

I must say I'm surprised at the number of tabs people have up - I rarely have more than 4.

I'm back with 3.6.16 at least that is stable. I see FFX 4 as the Windows ME of browsing.

It's not as if Mozilla didn't know about the problem, a Google for "Firefox 4 memory problems" shows posts dating back from early Betas

I have six tabs open and generally have 3-5. It's been sitting here since last night. I'm using 296Mb ram which is high for me on Windows. My wife and son both use FF4 also and, having just checked, are between 210 and 268Mb respectively.

No one I know ever complains about high memory usage in FF4 and neither have I experienced it since FF2.5 when memory leaks any user would notice were all fixed.

So my advice is the same. If your add-ons aren't causing you problems, fix your system.

I just installed 4.0.1 today on Mac and immediately I've come across this issue. FF can consume easily 800MB 5 minutes after boot. The number of tabs seems irrelevant since it occurs when I open both 5 tabs and 10 tabs. I turned off all plug-ins and add-ons but still see the same. Downgraded to 3.x.

For those of you with a 64-bit OS, you could try using a 64-bit version of firefox. I am running nightly 64-bit and having no memory leak or performance issues (had them with firefox 4 32-bit). With nightly tester tools, most extensions can be used. I think there is a 64-bit version of 4.0 too. Silverlight, flash and java are available, though I think some are in beta. Quicktime is not available.

I have the same exact issue.

Firefox 4.0.1 crashed at 1.8 GB of memory usage with only 4 add-ons on and 20 tabs open.

There seems to be a very serious memory leak here. Before it crashed, Windows popped up an out of memory error. Now that tells me something is wrong.

I also have 8 GB of RAM installed. Seems it's not enough for this browser.

I had this problem repaired in 3.6.14 with Bar Tab 2.0 add-on loaded. Bar Tab stops backround tabs from using CPU slices after a set amount of time. Only the current tab in focus gets CPU. Bar Tab is the only add-on that fails to upgrade with FF 4.0.1. NoScript, Better Privacy, FlashBlock and AdBlock help alleviate the problem and keep 25 tabs from growing to 800MB for about 30 hours but Bar Tab was the clear winner of a solution.

My solutions:

• Go back to FF 3.6.14 and use Bar Tab
• Have Memory Cleaner (part of Reg Toy utilities) running and use the Trim Process Working Set clear memory option to force FF to 18kb and let it reclaim only what it needed.

I'm waiting patiently for Bar Tab to be upgraded for use with FF 4. I'll just use other browsers or Memory Cleaner till then.

I downgraded back to FF 3.6.17. Firefox 4 was using 350 mb of ram with no extra tabs open, IE was using 57 mb. Now running Firefox 3.6.17 it is only using 36 mb of ram. Sure hope they get this fixed.

After reading this related article, I'm convinced uninstalling FF 4 is the best answer for now. Nothing like waking up to find your desktop bombarded with low memory pop-ups and crashed program alerts. Really makes me feel good about using Firefox...

I haven't taken a look at Opera in quite a while... hmmm....

I just thought I would add that developers are continuing to look at firefox and its memory usage. There are lists of

• known problems being investigated
• plans to reduce memory footprint
• new tools being proposed or offered.
  Firefox 5 users already have about:memory, key in about:memory in the location bar and hit return
  

nitrogenx, please stop trolling.

Alatari, there is a development version of BarTab out. You can install that on FF4