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firefox running slow after update, using lots of disk

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  • 1 has this problem
  • Last reply by philipp

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After the latest windows update, Firefox has been running unbelievably slow. I've tried refreshing, reinstalling, updating java, turning off windows defender, and just about everything else that's been mentioned on this site. Chrome/edge work perfectly, and the only suspicious performance issues involve my hard drive usage spiking to the 70% range whenever firefox is loading a page (albeit painfully slowly). Memory and CPU usage is similar across web browsers, but chrome/edge don't cause a spike in disk usage.

In addition to the slowdown, my bookmarks have all but vanished. Attempts to back them up result in a "unable to process this file" error message. I've tried uninstalling and deleting as many mozilla files as possible; program files, old data, etc.. prior to reinstalling, and still the same problem exists. Firefox still works wonderfully on my laptop, which hasn't been updated, but is seemingly permanently laggy on my desktop.

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hi hungryhank, thanks for the report - we're currently getting a couple of similar ones and looking into the matter in in case you're interested in following along. the issue is still a bit of a mystery at this point since it seems to affect only individual windows accounts on some machines...

if you want to downgrade to firefox 54 again in the meantime you can get the old versions from

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one more question: when you type "about:profiles" into your firefox address bar what is the full path of your profile shown in the root folder column?