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In the last week, Firefox slows down until it's unusable after about 30 mins


As per the title. Firefox slows down until it is almost completely unresponsive the longer it is left open. When it is restarted, it works fine for a while but soon slows down a lot.

I have about 50 tabs open and have never experienced this issue at all. I still have plenty of RAM free. When it's slow, even tasks such as opening menus or using the awesome bar slow down massively.

I suspect a tab is at fault but can't think of an easy way to determine which one.

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  • User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:19.0) Gecko/20100101 Firefox/19.0

More Information

  • Top 10 Contributor
  • Moderator
2054 solutions 8922 answers

hello, can you try to replicate this behaviour when you launch firefox in safe mode once?

Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

  • Top 10 Contributor
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10783 solutions 97057 answers

A possible cause is security software (firewall,anti-virus) that blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.

Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox and the plugin-container process and the updater process.


Helpful Reply

@cor-el - it's nothing to do with internet access. The program itself is unresponsive - I don't have any issue connecting to sites. As per my question: "When it's slow, even tasks such as opening menus or using the awesome bar slow down massively."

@madperson I will test that out.

  • Top 10 Contributor
  • Moderator
10783 solutions 97057 answers

Note that some security software may monitor Firefox because it considers the program as not trusted and may keep a log.
After using Firefox for a while that log may get so big that it slows the program.
In such a case it can help to make sure that the current Firefox version is fully trusted.

Try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.

Create a new profile as a test to check if your current profile is causing the problems.

See "Creating a profile":

If the new profile works then you can transfer some files from an existing profile to the new profile, but be careful not to copy corrupted files.

Modified by cor-el

Helpful Reply

I'm using the same antivirus for the last year and never had this issue before. Disabling antivirus doesn't help either.

Question owner

Firefox safe doesn't seem to make any difference :(

I've also culled all tabs opened in the last couple of weeks and got the total open down to about 25 so I don't think it's tab specific. It now takes about an hour to slow down meaning I have to restart the process more often that than. Very frustrating and inconvenient.

Has there been a recent update to Firefox?

PlaceboMessiah 0 solutions 7 answers

this exact same problem is also rampant on the Mac platform, i use no proxy or antivirus at all.

Question owner

I still haven't been able to fix this in any way :(