From MozillaZine Knowledge Base
bookmarks.bak is a Firefox backup of bookmarks.html in case of computer failure (ex: power outage). When Firefox is started and bookmarks.html is either missing or reduced to "0", bookmarks.bak will be used, if present, instead of the default set of bookmarks .
This file can be edited in the same manner as bookmarks.html, but there's no reason to do so.
This file can be moved to a different profile without any extra effort, but there's no reason to do so.
Deleting bookmarks.bak will have no effect except for losing a backup. The file will be regenerated, normally the next time Firefox is closed.
Related files and folders
- bookmarkbackups folder
Related bug reports
- Bug 218636 - backup bookmark file
- Bug 265120 - Bookmark backup is either broken or useless, bookmarks.bak is always a copy of bookmarks.html