Same problem. I have 4 gig machine running XP.

Monitoring Firefox in the Process view of Task Manager: starts out around 160,000k then increases to 200,000k where it plateaus for 1-5 min. After this there is a steady increase over the next half-hour to 1,500,000k - 1,800,000k (1.8 Gigs !!!) which is where it will freeze and I kill the process.

As far as addons, I am running firebug, ysolw, pagespeed, adblock plus and colorzilla. I have turned each off separately and rerun Firefox with same results.

My Process View makes me laugh :)

• Firefox . . . . . . . . . 1,600,000 K
• Visual Studio . . . . . .190,000 K
• Photoshop . . . . . . . .120,000 K

same here.. I actually have less add-ons than I did in 3.x cuz some were not compatible.

I installed the new version last night.. Went to bed, woke up in the morning and the browser is running sluggish. I look at it was using 1g of ram. Restarted FF and it's been running around 215-235mb for the last cpl of hours.

My firefox 4 was using 2 gb after 2 hours.

I'm using firefox 4 in a macbook pro with snow leopard

same. when go to lots of different pages that have lots of pictures in the same session, my total memory usage goes from about 550MB to over 1GB. only have 1GB ram so it start using virtual memory making it run slow. then i have to restart firefox to lower ram usage :(

In my experience, memory leaks are not uncommon in programs for Windows XP. It would be a good idea to reboot at least every couple of days. I reboot at the end of every day before I walk away. My machine runs like a top even though the installation is years old and has been through several motherboard changes without re-installation.

I'm running Windows 7 and the memory usage grows even with firefox 4 minimised, there is definitely an issue here.

I have also disabled all plugins and extensions other than: -Plugins: Sun JRE 1.6 u24, Sun Deployment Toolkit 6.0.240.7 - Extensions: Firebug 1.7.0 and LastPass 1.73.0

I'm not running a custom theme.

I have to agree. It does look like a memory leak and a pretty serious one. I've been running FF 3.x and updated it as new updates came around. Never really any issues.

Just updated to 4.0 and within the first hours I'm having trouble. FF became unstable, would respond slowly if at all to a close tab or window command (2 windows open, dozen tabs each) after a few hours of browsing. Looking at TaskManager FF sat > 500MB RAM.

After a fresh start I open taskmanager, then FF. Prior to the FF window coming to the front, it eats ~110MB RAM. Now with 6 tabs open into the session (1 google search FF4 memory leak, 4 support.mozilla pages and 1 gmail) it is at 222MB or RAM ... and keeps ticking up about 20-25KB/s ... without doing anything other than typing in this window ... and even when I pause for a few minutes ... it's up another few MB. Right now 233MB. That's 11 MB over the last typed line! Well 235MB since I typed that. No correction 237MB.

If that's not a memory leak, then I don't know what it is. (241MB)

Half of my extension were disabled btw with the FF4 upgrade.

Only have AdBlock Plus, ForecastFox, FireShot and FireBug as approved add-ons.

Pretty plain vanilla Windows Netbook with XP, 1GB RAM ... primarily used as email & browsing machine.

I've figured out your problem. The common issue I see with all of these cases is that you people are using Firefox. You need to install Microsoft Internet Explorer.

Got the same problem here, and it's only come up since upgrading to Firefox 4. Windows 7 with SP1, AMD Athlon X2 Dual-Core QL-65 (2.1 GHz), 4 GB Ram... Been using Mozilla/Firefox for well over a decade now, but if this isn't resolved soon, I will be abandoning it and going to IE8 :(

I have Firefox 4 on both win32 and linux (Fedora 14, build from remi repo). Both have NoScript and Adblock Plus installed, and no other extensions. The linux build is quite stable, but win32 build is not. With win32 build, the tabs are not so responsive to click or close, and sometimes Firefox 4 crash.

I'm reading a similar report on another forum https://adblockplus.org/forum/viewtopic.php?f=1&t=7006&sid=cb5583f99d76444e1161968aa729778e

With Adblock Plus 1.3.5 only or PageSpeed 1.10.2 only I don't have any issue. But with the two installed I have memory leaks.

Firefox 4, Windows Vista SP2, Adblock Plus 1.3.5, PageSpeed 1.10.2

Pretty much the same story here. I start at the beginning of the day with low memory usage, and by the afternoon (or sooner) I see a huge slow down in FF4 and 1.75GB of memory usage. Waaaaaay too much. Even for 4 windows, and a combined 25-30 tabs.

Using FF4 in Mac OS X 10.6.4 with addons Adblock Plus, Xmarks, Firebug, Web Developer, Better Gmail 2, Shorten URL, Siphon, User Agent Switcher.

Memory leaks here too - Windows 7 x64. Starting firefox 4 in safe mode, firefox's memory consumption will increase by 1MB every 7 seconds. Firefox will also hang quite often for short periods of time, sometimes it even disappears entirely and then reappears. This was with 4 tabs open. Had memory leaks and hang-ups with firefox 3, but not this severe.

not so bad here, only using 1.7G  :O Open for about 2 days.

I just disabled 6 of the 9 extensions I have in hopes that will make FF usable.

It would be helpful if Mozilla could provide a memory profiling tool that would help us civilians track down memory problems either in the core products or in extensions. The suggestions to create new profiles, re-add extensions, and do A/B (C/D/E) testing along the way, while accurate, aren't practical when we discover that FF 4 on Win 7 is using north of 1GB of memory.

It looks like it's firebug - I have ran firefox 4 all morning without firebug open, no memory problems, use firebug with some jquery development - boom straight up to 1.5Gb within an hour or two.

I had turned firephp off a few days ago - hoping it was that.

OS: Linux (Ubuntu 10.04) RAM: 4Gb

I'm using a Macbook running OS 10.6.7 with 2GB RAM. I was so excited when FF4 was released cause I've been with firefox for a long time. But now I don't dare to use it as my main browser (only use for web developing purpose) because it consumes my system memory like hell. Last time I opened about 10 tabs and after 1 hour, it reached 1GB and nearly froze my computer. Yesterday I tried to open 1 (which is a localhost tiny site) and after that it still could manage to climb to >200MB. I had the memory leak issue with FF3.6 but it was still acceptable but for this version, it is not tolerable. Hope Mozilla can fix this soon.

I used this tool a couple of versions ago to track a couple of extensions that were causing excessive memory usage for me. It was designed to find JavaScript objects leaks in Firefox chrome and web sites, so it isn't a total leak detection tool.

https://addons.mozilla.org/en-US/firefox/addon/leak-monitor/
http://dbaron.org/mozilla/leak-monitor/

IMO, if you need Firebug for your work, install it in a separate Profile that you don't use for everything.

Create a new profile for Firebug and also create a desktop shortcut with -P "profile" appended to the "target" line to launch that profile. The -no-remote command line parameter in the "target" line will allow you to launch that Profile while another Firefox Profile is running.

• http://kb.mozillazine.org/Creating_a_new_Firefox_profile_on_Windows
• http://kb.mozillazine.org/Shortcut_to_a_specific_profile
• http://kb.mozillazine.org/Using_multiple_profiles_-_Firefox

Workaround found: Open about:blank in one tab and the memory leak is gone. If memory still grows refresh about:blank to free memory.

Admittedly I have a large number of tabs open but FF 3.6.x used to consume up to around 1GB of memory... Rarely seen it reach 1GB but just yesterday on FF 4.0 I managed to hit near 1.6GB! Heh.