It might. But, it might not. Sync is not meant as a backup. You should copy all files on your hard drive that you want to an external hard drive. This is another way; Type '''about:support'''<enter> in the address bar. Under the page logo on the left side, you will see '''Application Basics. ''' Under this find '''Profile Folder. ''' To its right press the button '''Show Folder. ''' Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder '''Linux: ''' Under the page logo on the left side, you will see '''Application Basics.''' Under this find '''Profile Directory. ''' To its right press the button '''Open Directory. ''' Now '''Close Firefox. ''' This is your current profile. Copy the folder '''As Is''' to a folder on a thumb drive. Then '''Copy''' the folder to the new system.

See also: *https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles *https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile