If you use Time Machine on a Mac to back up your data, then you might have also seen an increasing amount of locally stored backups occupying room on your hard drive. This isn't a glitch in the system, but simply how Time Machine works. Should you want to reclaim that space, here's how it's done.
For those yet to explore the virtues of this helpful utility that comes free with all macOS devices, take a look at our How to use Time Machine to back up a Mac guide.
Why are there backups on my Mac?
While Time Machine uses external drives to store backups, there's also a component to the software that records any changes to your system and stores them on your internal storage. Apple calls these 'local snapshots' and says they are there to protect your data whenever you haven't got an external drive connected.
This might seem somewhat presumptuous of Time Machine, but the local snapshots are not treated the same way as normal data on your device.
macOS monitors how much space is being used by these files and should immediately delete them to make way for other things, such as programs you want to install, without you even knowing. Older snapshots are also periodically deleted to preserve your storage capabilities.
If you launch the Time Machine app without a drive attached to your Mac, then it will use the local snapshots to restore data and files that you're hoping to recover.
See How to restore files from Time Machine for a more complete overview of how the app works.
How can I delete the local snapshots?
There are two main methods for removing local snapshots from your hard drive. The first is to simply turn off the Time Machine feature itself, which will then delete all of the local snapshots stored on your Mac.
To do this, open System Preferences, select Time Machine, then untick the Back Up Automatically box.
Apple recommends giving it a few minutes for the local snapshots to be deleted, then you should see the space reappear on your hard drive.
The second route is for when the first fails, but it's not one we'd recommend to someone unfamiliar with the command line and only seems to work on systems running macOS 10.12 (Sierra) or earlier. So, if you're not confident using code it's probably better to try the first step a few times again and then maybe contact Apple Support to see if they can help.
If you're happy to continue then open the Finder and navigate to Applications > Utilities > Terminal.
Now enter the following command, pressing enter at the end:
sudo tmutil disablelocal
This will, as the last word suggests, disable the local snapshot feature in Time Machine, preventing it from creating any new ones and removing all that already exist.
Should you want to re-enable the feature at any point then repeat the process above, but this time use the following command:
sudo tmutil enablelocal
Hopefully one of these methods will give you back the space you need on your Mac. For more options when it comes to keeping your data safe, you can also read our How to back up a Mac guide.