I am using Ccleaner 6.06. I just noticed under Applications/Firefox that something called Bookmarks backup is checked and so being cleaned. I don't recall bookmarks backup being an option in older versions and I am not sure if its something I want to keep checked and cleaned or ???
So what is it cleaning and do I want to keep cleaning it?
It was added a few CCleaner versions ago, so yes it's a fairly new option.
Ticking it for clearing simply removes the automatic backups of your bookmarks that Firefox makes everytime you add a new bookmark or remove an old one.
It only clears those automatic backups, it doesn't touch your current bookmarks.
Whether you clear them or not with CCleaner is of course your choice.
Personally I make a lot of bookmarks that I'll only use for a day or week, so I prefer keeping a manual backup file of just my main bookmarks, rather than some temporary backups that Firefox keeps changing anyway as I make and delete bookmarks.
I would advise that you prevent CCleaner from cleaning your Firefox bookmark backups unless you are critically low on free disk space. If your Firefox bookmarks are ever corrupted or go missing you can restore them from a recent backup (Bookmarks | Manage Bookmarks | Import and Backup | Restore) as described in the Mozilla support article Restore Bookmarks From Backup or Move Them to Another Computer. As nukecad noted, Firefox only keeps ~ 15 of the most recent bookmark backups and regularly purges older backups, and my bookmark backups use less than 15 MB of disk space.
Firefox automatically backs up my bookmarks approx. every 3 or 4 days on my system and saves the .jsonlz4 file in my Firefox user profile in the hidden folder C:\Users\<<em>myusername</em>>\AppData\Roaming\Mozilla\Firefox\Profiles\<<em>firefoxuserprofilename</em>>\bookmarkbackups. I go one step further and manually backup my Firefox bookmarks (Bookmarks | Manage Bookmarks | Import and Backup | Backup) about once a week and save them to a removable USB thumb drive just in case some disaster happens and I am unable to restore the most recent bookmark backup stored in my Firefox profile (<em>note: if you are creating important bookmarks that you don't want to lose then a weekly manual backup may not be frequent enough for you</em>). If you are critically low on free disk space and allow Firefox to clean your bookmark backups just be sure you ways have a recent manual backup of your bookmarks safely stored somewhere like a removable USB thumb drive.
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