I just installed Firefox 12 and memory usage on 40 open tabs spiked from a maximum of 900 MB-1 GB to 2.5 GB. Memory usage for firefox.exe would start at 4-500 MB, steadily increase to 2.5 GB in 10-20 min even if I did not touch the browser at all. Hard drive I/O went trough the roof as well. Laptop would become unresponsive and Firefox would eventually crash. Downloaded Firefox 11, installed it on top of Firefox 12 and everything is back to normal, memory usage is less than 900 MB with normal usage, it doesn't really grow past that. Guess will stick with 11 until they fix these issues in 12.
Upgrades tend to fix security problems, so it is not recommended to use unsupported versions, as Firefox 11 now is. Developers are working to reduce memory usage,and I am not aware of anything expected to increase memory usage in Firefox 12 and certainly it should not be crashing.
The problem may well relate to some software extension or site behaviour rather than Firefox itself. (If that is the case then waiting for a Firefox fix may not help)
You can still try to disable the other extensions or create a new (test) profile.
Create a new profile as a test to check if your current profile is causing the problems.
See "Basic Troubleshooting: Make a new profile":
There may be extensions and plugins installed by default in a new profile, so check that in "Tools > Add-ons > Extensions & Plugins" in case there are still problems.
If that new profile works then you can transfer some files from the old profile to that new profile, but be careful not to copy corrupted files.
@John99 I took the memory usage from the Task Manager, Working memory set for firefox.exe. I didn't have time to do more troubleshooting and I doubt i'll have time to do more over the next week but something is very very wrong with this version. I mean, the memory utilization is just insane. Normally, the Task Manager Memory utilization history graph is flat. With Firefox 12 it's growing linear, then at some point it has a sharp drop, then it continues the linear growth and it doesn't stop until it crashes. It crashed on me 5 times in 3 hours. I don't remember any previous version crashing this much. To top it off, it's trashing the hard drive continuously even if i'm not doing anything. All these issues disappeared once I installed v11 back.
This bug sounds similar to what i'm experiencing:
As for running a version with known security vulnerabilities, Firefox 11 has 5 critical vulnerabilities and 3 moderate ones reported, Firefox 12 has 7 critical vulnerabilities, 4 high and 3 moderate. The way I see it, i'm safer running 11 than 12. Going to wait for a patch over the next week, after that i'm switching to Chrome..
Sorry I am no security expert, but my rather naive logic is that
If you use out of date unsupported software you need to be prepared for the consequences.
Firefox & Memory
Unsupported Firefox 11
Even if there is a fault in Firerfox 11 that version is unsupported, Unsupported implies
These are something that I think MozillaFirefox would like to look in to, with the aim of reducing the number of crashes. Unfortunately Firefox is used with masses of other software. It is still a Firefox crash and a Firefox problem, but priority is, I suspect, likely to be given to crashes that occur in Troubleshoot Firefox issues using Safe Mode or with only a single software extension.
Maybe you will have time to look at things later. Sometimes Firefox does have regressions and problems that are overlooked or dismissed initially but are real. That has happened before with memory problems and hangs. They can not yet monitor memory in the same way as crashes. They do now have telemetry in place to monitor hangs. A FAIK all we have with memory problems is about:memory in the User Interface.
What I am trying to say is that sometimes it takes quite a bit of effort in order to demonstrate a reproducible problem that developers are able to investigate. If
Its true that firefox has this problem. It makes the processor run like anything and makes the CPU fan work at its full efficiency. However, 11 was no better. 11 was having a memory issue as well. I was hoping that 12 would fix that but it didnt, unfortunately.
Anyone with problems
Please start your own thread by following the links and prompts from:
If you just wish to register feedback instead of asking for a solution then please try
Same issue here - massive memory use - upgraded to 12 and at the same time halved the no. of add-on to 8, but memory use has increased.....regularly sits at about 750 real / 750 virtual with 12 tabs (Mac Activity monitor). Opening 12 tabs from scratch will put the computer out of use until loading has finished.
PS. I'm guessing here but I'd reckon that most Firefox users are not on 12 yet so......this is a little harsh...... "If you use out of date unsupported software you need to be prepared for the consequences. "
I can not recall mention of any change between firefox 12 and previous versions that makes it much worse for memory usage .
Read this thread for information, but as advised previously, if you have a problem please then start your own thread by following the links and prompts from /questions/new
There is a recently started program of continuing efforts by developers to improve Firefox's memory usage. This includes improved tools, to try: key into the address bar about:memory you will get interactive information about memory use, with a button to reduce it.
With the fast release development cycle the improvements will not normally be made to older versions.
Telemetry has been added, this collects real world information on real users (anonymised and respecting privacy) and includes things like startup times, memory usage and information on hangs this allows developers to monitor improvements and watch for any inadvertent regressions that cause problems. It would help if as many users as possible opt in for this see
I am not sure where the stats are on usage numbers of the versions, but if previous trends are anything to go by then a lot of users will be on the latest version.
 There are some stats on memory use, I think sumarised as firefox 12 could be 10% worse than firefox 10 but doubling addons increases resident memory by 33% . But with a caution that there is a great variability in results. This thread would not be the place for discussion of the stats, but I add the note to show that information is collected and studied, if users will opt in to provide the info.