I have a 256GB SSD which usually sits at around 30GB available space, but recently I've had a problem with what appears to be over zealous caching which has on a number of occasions eaten the entire 30GB.

Last time it happened my system was grinding to a halt with no space left at all, its amazing what breaks when there's no disk space, so I just deleted the offending files. This caused issues with my Keychain but I managed to recover.

Yesterday I got the warning again, and I was down below 10GB, I'm now sitting at 18GB without deleting anything since, so it seems to be rapidly up and down.

I've used Disk Inventory X to investigate and the culprit seems to be the folder:


Currently there's 30,110 files in that folder using up 8.8GB, which seems a little excessive on its own! I'm pretty sure thats the same folder that eventually swells to fill up my HD.

As far as I know, WebKit is safari's engine? I use 4 Safari extensions which are: 1Password, AdBlock, BetterTTV and Reddit Enhancement Suite.

Any idea what specifically is causing this? or how I might identify the culprit? I'm also on Sierra 10.12.2 beta.

  • 1
    You might want to boot the Mac in Safe Mode (hold down Shift key after startup chime) and have the OS delete a slew of cache files for you. This doesn't attempt to answer your question, but at least you won't be deleting files that cause Keychain issues. In addition, perhaps the Sierra beta release has something to do with this problem, and it will go away with the next public release.
    – IconDaemon
    Dec 2, 2016 at 14:59

2 Answers 2


I had the same problem; wrote the following bash script and run it once daily with cron. Problem solved. When I first noticed this, I had over 50GB in the fsCacheData folder!

SIZE=$(du -h $DIR | cut -f 1)           

if [[ "${SIZE%?}" -ge $LIMIT ]];
    rm -r $DIR

I have noticed that every now and then, the built-in verification for Time Machine appears to get jammed on my Mac. If the following Terminal command returns a result:

find /var/db/com.apple.backupd.backupVerification -type f

while Time Machine claims to be idle at the same time, it’s probably safe to delete the contents of /var/db/com.apple.backupd.backupVerification. I have reclaimed several dozens of GB in the past that way.

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