If you have sync, and there is a problem anywhere, '''Shut Down Sync Immediately On All Devices''' to prevent the problem from spreading. Type '''https://accounts.firefox.com/settings'''<enter> in the address bar. Once the problem is fixed, perform the same repair on all computers/profiles before using sync again. [v57+] Places Maintenance is built into Firefox&#46; Type '''about:support'''<enter> in the address bar&#46; You will find '''Places Database''' near the bottom&#46; Press the '''Verify Integrity''' button&#46; If any errors are reported: https://support&#46;mozilla&#46;org/en-US/kb/fix-bookmarks-and-history-will-not-be-functional The '''places&#46;sqlite''' file contains your History and Bookmarks&#46; And it looks like it is corrupted&#46; Type '''about:support'''<enter> in the address bar&#46; Under the page logo on the left side, you will see '''Application Basics&#46; ''' Under this find '''Profile Folder&#46; ''' To its right press the button '''Show Folder&#46; ''' This will open your file browser to the current Firefox profile&#46; Now '''Close Firefox&#46; ''' Locate the above file&#46; Then rename or delete it&#46; Restart Firefox&#46; The browser should then create a new place&#46;sqlite and recover your bookmarks from the backup files&#46; Note: Your history is not backed up and will be lost&#46;