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Update 40.0.2 is slow, hangs a lot, even in safe mode.

  • 23 replies
  • 9 have this problem
  • 7 views
  • Last reply by cor-el

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So, i tried several things in the troubleshooting articles here in the Support, but none solved my issues.

Basically, after Firefox automatically updated to 40.0.2, the browser hangs a lot on opening and closing tabs, as well loading websites. When not doing anything, the CPU/RAM usage is normal, but opening or closing tabs uses a lot of CPU (most of the time, 100% of the CPU is being used when browsing) and it hangs every time. Scrolling down pages also causes the browser to hang. I tried disabling several plugins and extensions and I even tried using safe mode, but even in safe mode it happens constantly. I'll post the specs of my computer (not big deal), but remember that these issues didn't happen before the update.

Core 2 Duo, 2.93 GHz 4 GB RAM Windows 7 Ultimate 32-bit GeForce 8400GS

Please, did anyone find problems with this new update? What should I do? I've been using Firefox since 2007 and I love it, I'd hate to switch to another one.

So, i tried several things in the troubleshooting articles here in the Support, but none solved my issues. Basically, after Firefox automatically updated to 40.0.2, the browser hangs a lot on opening and closing tabs, as well loading websites. When not doing anything, the CPU/RAM usage is normal, but opening or closing tabs uses a lot of CPU (most of the time, 100% of the CPU is being used when browsing) and it hangs every time. Scrolling down pages also causes the browser to hang. I tried disabling several plugins and extensions and I even tried using safe mode, but even in safe mode it happens constantly. I'll post the specs of my computer (not big deal), but remember that these issues didn't happen before the update. Core 2 Duo, 2.93 GHz 4 GB RAM Windows 7 Ultimate 32-bit GeForce 8400GS Please, did anyone find problems with this new update? What should I do? I've been using Firefox since 2007 and I love it, I'd hate to switch to another one.

Chosen solution

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

See "Creating a profile":

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.


Boot the computer in Windows Safe mode with network support (press F8 on the boot screen) to see if that has effect.

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It is likely that there has been a problem with the places.sqlite file if restoring this file brought back the slow response.

You could have just removed all places files (places.sqlite and places.sqlite-shm and places.sqlite-wal) to undo this action. If the places.sqlite is corrupted then your history is lost. You can recover the bookmarkbackups folder with the compressed .jsonlz4 backups to restore the bookmarks.

  • bookmarks-YYYY-MM-DD_<item-count>_<hash>.jsonlz4

You can use this extension to check for problems with the places.sqlite database file (bookmarks, history) in the Firefox profile folder.

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It's okay like this, I guess the history wasn't that important, but thank you. I'll be setting this post as Solved. Thank you for everyone who helped.

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You're welcome.

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