Note that Firefox keeps a full undo stack of changes to bookmarks for the current session. So if you haven't closed Firefox, you can open the Bookmarks Manager (Library; Ctl+Shift+O) and use "Organize -> Undo" (Ctrl+Z) until you see the deleted bookmarks reappear. Firefox keeps automatically creates backups in the bookmarkbackups folder, so you should be able to restore the bookmarks from a recent backup. See " My bookmarks have disappeared": *https://support.mozilla.org/en-US/kb/recover-lost-or-missing-bookmarks The name of an automatically created JSON bookmarks backup in the bookmarkbackups folder includes a total item count (folders and separators included) and an hash value to prevent saving the same backup more than once. You also see this count in the Restore menu drop-down list. *bookmarks-YYYY-MM-DD_<item count>_<hash>.jsonlz4.