Bookmarks are like Gold in the online world. It can take years to compile a list of precious bookmarks and it is a huge catastrophe for most users if the collected bookmarks happen to be gone.
There are several scenarios that I can think of that would make the bookmarks disappear in Firefox.
The file could be corrupted, a sync error could be the cause, an extension or third party program could have moved, renamed or changed the file so that Firefox can't read it anymore, or your hard disk could have a read error in that sector.
Don't loose all hope yet, there is a good probability to get the Firefox bookmarks back.
First, close all instances of Firefox immediately and make sure that no Firefox tasks are open in the Task Manager. You can verify that on Windows by using Ctrl-Shift-Esc to open the Task Manager.
Make also sure that no third-party tools that manipulate Firefox are open. (Browse this website with Opera or save the information to your hard drive in a text file).
Firefox creates backups of your bookmarks. I hear sounds of relief already. The backups are located in your Firefox profile folder in the subfolder "bookmarkbackups". The file name includes the date the backup was created, but you can't launch the file directly.
Tip: open about:support in the Firefox browser and click on the "open folder" button to open the profile folder using the operating system's file manager.
A new backup is generated regularly and Firefox keeps several bookmark copies as backups.
Please note that Mozilla changed the format of the file it saves bookmarks in from HTML to JSON. While that is beneficial for a lot of things, it limits your options in regards to restoring bookmark backups in the web browser.
You can copy any of the backups created automatically and move it to another location for safe keeping as Mozilla Firefox will delete old backups eventually.
Now that you know that bookmark files are available, hopefully, you may import them in Firefox.
If you have a bookmarks.html file, for instance from another browser's backup or from Firefox, you may import it as well. Select Import Bookmarks from HTML instead under Import and Backup to load such a file in Firefox.
Another option would be to check if you are using the correct Firefox profile. Remember that every profile has it's own set of bookmarks.
Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers.