If you used the delete all data, or whatever the wording, because you did an uninstall then you will need luck and a file recovery program. It sometimes works out [/questions/787020#answer-141048 see]. If you did a standard upgrade Firefox tries to save all such important data. It could also have helped if you had made separate [[Backing up and restoring bookmarks|manual backups]]. Normally bookmarks are not lost, or Firefox has kept some auto backups from which you may be able to restore most of your * [[Lost Bookmarks]] <-- click the link for instructions ---