File extension .BAK is used by Firefox Web browser to provide a backup for the bookmarks file of the user. Extension .bak is automatically generated by Firefox to replace the bookmarks in case the main file becomes corrupted.
NOTE: The file extension should be changed back to the original extension in order for the file to open correctly. This is often done by simply removing the “.bak” part of the filename. For example, “mydocument1.doc.bak” should be renamed to “mydocument1.doc” before being opened.
When the Firefox program is installed in the system, it will create another instance of the file bookmark.html and name it bookmark.bak.
In case the file bookmark.html gets corrupted, Firefox immediately retrieves the data contained in the file bookmark.bak and renames it to become the new bookmark.html file.
The backup function of the file extension BAK is important in securing data from within the system.