This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

The longer Firefox is running, the slower it gets (FF 18, 19)

  • 10 replies
  • 30 have this problem
  • 1 view
  • Last reply by boggled123

After starting Firefox, it begins to slow down after 15 minutes or so, until it is so slow that I have to re-start it. After that, it runs fine at first and then slows down again.

  • This started with version 18, and the problem continues with version 19.
  • It slows down whether I am using it or not. I can start Firefox, walk away, come back in half an hour and it's too slow to use.
  • Nothing else on the computer is slow, only Firefox.
  • It slows down even with all plug-ins disabled.
  • By "slow down" I mean a delay between typing a letter and seeing it appear, scrolling (with mouse wheel, scrollbar, or arrow keys) becomes difficult and then impossible, reloading a tab causes the animated activity indicator to appear but it slows down to a stop and the page takes forever to reload, etc.
  • Never had this problem until FF18.
  • I'm using Windows 7 Home Premium 64-bit, 4GB RAM

Help?

After starting Firefox, it begins to slow down after 15 minutes or so, until it is so slow that I have to re-start it. After that, it runs fine at first and then slows down again. * This started with version 18, and the problem continues with version 19. * It slows down whether I am using it or not. I can start Firefox, walk away, come back in half an hour and it's too slow to use. *Nothing else on the computer is slow, only Firefox. *It slows down even with all plug-ins disabled. *By "slow down" I mean a delay between typing a letter and seeing it appear, scrolling (with mouse wheel, scrollbar, or arrow keys) becomes difficult and then impossible, reloading a tab causes the animated activity indicator to appear but it slows down to a stop and the page takes forever to reload, etc. *Never had this problem until FF18. *I'm using Windows 7 Home Premium 64-bit, 4GB RAM Help?

All Replies (10)

  • Check your Antivirus/Firewall not blocking your firefox
  • check your plugins are updated
       *https://www.mozilla.org/en-US/plugincheck/
  • Goto Firefox File Menu > Exit.
  • Clear cookies and give a try...

I thought I was crazy. I pared back all my plugins to just gestures and adblock plus. If my Linux Ubuntu FF 19.0 sits overnight, opening a new tab takes 30 seconds!!! And it's just completely sluggish. I must restart FF to get back to normal performance.

FF slowly starts taking over 100% CPU during this time as well.

If it is a memory related problem note that Firefox now interactively produces detailed information type into the location bar

  • about:memory
  • and maybe also try about:compartments

On mouseover tooltips may appear giving further information.

You should also turn on telemetry

  • that provides developers with information
  • it provides masses of complex information you may look at yourself, at least it allows you to quantify what is going wrong (use about:telemetry)
  • see Share data with Mozilla to help improve Firefox

I will enable telemetry and keep a watch on memory and compartments to help y'all debug this issue.

Just FYI, I've NEVER had any problems with FF eating up memory and CPU like this until FF 18 or 19.

Have a look at the memory reports, is the amount of memory Firefox uses increasing. If you look in Windows task manager does that show a large amount of memory used, and also does it show that you are paging memory.

How much RAM is installed on your computer. How much space is left on the HDD both as amount in GB and as a percentage of the drive.

Note this problem is possibly something fairly unique to you, it is unlikely to be affecting the majority of users or even the majority of Windows 7 users.

You should also try Firefox in safe mode, with just the default theme, and with all plugins disabled, does that help ?

Do you notice any pattern to this ? Is it for instance only after you use video content, or when very many tabs open. (hundreds)

@iamjayakumars

Thanks for the suggestions. How do I check whether my firewall/antivirus is blocking Firefox? I'm using AVG antivirus.

Aside from that, I've done everything you recommended and FF still slows down.

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

How do I determine whether my firewall or antivirus are "blocking Firefox?"

Does the fact that Firefox works (albeit slowly) indicate that it is not blocked?

I'm using AVG antivirus.