If you care for the fix to this I will give that also : Please update to 57.0.2 https://support.mozilla.org/en-US/kb/update-firefox-latest-version fyi: There was a issue with too much ram being used which caused slowness as being one of the issues. This was fixed by posting here and asking for help but was fixed in version 57.0.1 There is another fix which you can adjust the multiprocessor use : You could try this please : Go the Menu then Tools --> Options --> Performance and untick everything. change the recommended size lower then see how it runs. Note: 0 = No Multi-processor = slow again. Try 2 Restart Firefox after making these changes please. Going back : unfortunately 56.0.2 and below is no longer safe to use for every day use do to secuity issues, but 52.5.0 ESR is. It will continue to get security updates until May 2018, and you can download and install it from this page: https://www.mozilla.org/en-US/firefox/organizations/all/ <b>Note : Legacy Extensions will be deleted or removed in any version update after May 2018</b>. You should make a backup of your Profile before going back and just because: https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles 57+ and going back incompatible profile. https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer Please let us know if this solved your issue or if need further assistance.

Thanks for the info pkshadow. I ran security scan, cold booted, updated to 57.0.2 and browser seems to be working at 'normal' speed. Happy Holidays!!