If the back up does not work, it is possible to open the file in a text editor and open all the urls, however that is tedious. What is the file extension and what steps are you taking to restore them? This might clear up the error.

You can check for problems with the <b>places.sqlite</b> database file (bookmarks, history) in the Firefox profile folder. *Places Maintenance: https://addons.mozilla.org/firefox/addon/places-maintenance/ *http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox *https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file Remove all places.sqlite file(s) in the Firefox profile folder to make Firefox rebuild the places.sqlite database from the most recent JSON backup (bookmarks-YYYY-MM-DD_<item-count>_<hash>.json) in the bookmarkbackups folder. You may have to restore an older JSON backup. *http://kb.mozillazine.org/Unable_to_process_the_backup_file_-_Firefox You can use this button to go to the current Firefox profile folder: *Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder) *http://kb.mozillazine.org/Profile_folder_-_Firefox Note that the name of a JSON bookmarks backup file includes a total item count (folders and separators included) and an hash value to prevent saving the same backup more than once. *bookmarks-YYYY-MM-DD_<item count>_<hash>.jsonlz4.