Public service announcement for photographers and anyone that add and delete lots of files on their Apple Mac computers.
If you’re using a Mac, and your disk seems to be filling up even though you’re deleting files, check if you’re using Time Machine (TM) for backups. If you are, Time Machine’s Snapshots is 99% going to be chewing up your disk. Here’s why…
Snapshots is macOS approach to create a restore point so you get your Mac to a known state. It does this by combining the last TM backup with a snapshot. The backup has all the files just before the snapshot and the snapshot has all the files that you have deleted since the backup.
So, let’s say you’ve just copied from your camera 1000 photos for editing and have now decided to move those 1000 photos to an external disk, NAS or just delete them. Even though you’ve deleted the 1000 photos, macOS has kept them in the Snapshot, and will keep them in Snapshots until a TM backup has been done. It will still keep those on your disk until at least 24 hours after the TM backup, because that’s what it does. So your 256GB or 512GB SSD is going to fill up pretty quickly and deleting files isn’t going to get you back your disk space until you’ve done a TM backup, and then 24 hours later.
But, luckily there’s a simple solution. Go into the Disk Utility App and choose Show APFS Snapshots in the View menu. Select your disk and you’ll see probably several Snapshots. Click on the – sign and you can delete the snapshots, start with the most recent going back to the earliest. And Voila. Disk space reclaimed. Of course, if you do that, you won’t be able to recover the files in the snapshot. But since you deleted them anyway, you probably don’t want them.
And, the way to avoid this and keep using Time Machine is to create a separate disk Volume that is excluded in Time Machine backups. You need to create a separate volume because excluding a Folder in TM won’t stop TM keeping the deleted files in the snapshot, it just stops TM from backing up that folder.
More technical details about snapshots here https://eclecticlight.co/2024/04/08/apfs-snapshots/