Using a full profile especially if it comes from another device isn't recommended and can cause all kinds of issues that are hard to troubleshoot. Best is to revert to the original profile that worked fine or create a new profile and only restore personal data you really need.

You can copy certain files with Firefox closed to the current profile folder to transfer or recover personal data. Note that best is to avoid copying a full profile folder. Note that you should be cautious with copying SQLite database files if you previously had problems.

• bookmarks and history: places.sqlite
• favicons: favicons.sqlite
• bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
• cookies.sqlite for the Cookies
• formhistory.sqlite for saved autocomplete Form Data
• logins.json (encrypted logins;32+) and key4.db (decryption key;58+) for Passwords saved in the Password Manager
  key3.db support ended in 73+; to use key3.db in 58-72, make sure to remove key4.db
• cert9.db (58+) for (intermediate) certificates stored in the Certificate Manager
• persdict.dat for words added to the spell checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
• sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

By “Glitter” you mean random pixelated chunks across the entire app window that change with screen / mouse movement?

I have this and it makes Firefox unusable. It disappears in safe mode. But with ALL extension removed, still occurs.

By “Glitter” you mean random pixelated chunks across the entire app window that change with screen / mouse movement? I have this and it makes Firefox unusable. It disappears in safe mode. But with ALL extension removed, still occurs.

Thanks for the reply, but it was certain bits glittering, like someone's head, or a piece of clothing on someone, or a particular building. It was very strange. I now have a new profile and it doesn't happen any more.

Hi rranslam

You can try to disable hardware acceleration in Firefox.

• Options/Preferences -> General: Performance
  remove checkmark: [ ] "Use recommended performance settings"
  remove checkmark: [ ] "Use hardware acceleration when available"
• https://support.mozilla.org/en-US/kb/performance-settings

Close and restart Firefox after modifying the setting for changes to take effect.

• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

You can check if there is an update for your graphics display driver and check for hardware acceleration related issues.

• https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration