Time Machine doesn’t just back up to external drives. Enable Time Machine on your MacBook and it will create “local snapshots,” too — potentially taking up over 100 GB of disk space on its internal storage.
These local snapshots appear as “Backups” when you look at the visual overview of storage in the About Your Mac window. Here’s how you can free up that space and get more room on your Mac.
To see how much space those local Time Machine backups are consuming, click the Apple icon on the menu bar, click About This Mac, and click the Storage heading. The “Backups” category here represents your local snapshots. You can’t normally see or access these backup files — use the commands below if you need to quickly remove them from your Mac’s internal storage.
Local snapshots are only created if two things are true. First, you must be using a Mac notebook and not a Mac desktop PC. Second, you must have enabled Time Machine to back up to an external drive. If you’re using a desktop Mac with Time Machine enabled, or if you’re using a Mac notebook with Time Machine disabled, your Mac won’t bother creating local snapshots.
These snapshots are designed to help you recover deleted files or previous versions of files, even if your laptop is away from its Time Machine drive for a while. Your Mac automatically creates them in the background, and the Time Machine icon on your menu bar won’t even say it’s doing anything as it does so. These local snapshots are stored on your Mac’s startup partition along with all your other files.
You can open Time Machine and restore those files, even if you haven’t actually plugged in your drive and performed a Time Machine backup in a while. You can also recover previous versions of files from your Mac’s local snapshots if you don’t have your Time Machine drive with you. It’s a safety net designed for portable laptop use.
To take advantage of those local snapshots, just open the Time Machine interface and try to restore an old file. You’ll be able to do so without plugging in your Time Machine drive, as long as that old file is part of your local snapshots. For example, in the screenshot below, a snapshot was taken earlier in the day at 1:58 pm. The Time Machine drive wasn’t plugged our MacBook at this point in time, so that’s a local snapshot stored entirely on our Mac.
This is a useful feature, but it’s counterintuitive. You probably expect Time Machine to back up primarily to an external drive, so opening up the disk space usage window and seeing local backups taking up gigabytes of precious space on your Mac’s drive can be confusing.
However, your Mac does tell you it keeps these backups — it says it keeps “Local snapshots as space permits” in the Time Machine window.
The “as space permits” bit is the key here. When less than 20 percent of the space on your Mac’s startup disk is available — or if less than 5 GB of space is available — your Mac will start automatically purging the oldest Time Machine local snapshots to free up space. At less than 10 percent or 5 GB available, your Mac will become even more aggressive.
In theory, you shouldn’t have to worry about how much space is being used for backups. Your Mac will use spare disk space for backups, just to be safe, and free up that disk space for other things when you need it.
This will work for most people, but it can sometimes cause problems. If you want to shrink your Mac’s disk partition, create a full disk backup, or start installing a massive game or other piece of software that needs a lot of disk space available, those local snapshots can get in the way. Here’s how to purge them.
If you opt to disable Time Machine entirely, your Mac will remove those local snapshots, too. But this isn’t necessary, and you probably don’t want to do it this way.
There is a way to delete only the local snapshots, although Apple doesn’t make it easy to find — it requires using a terminal command. Open a Terminal window by pressing Command+Space, typing Terminal, and pressing Enter. Type the following command into the terminal and press Enter:
sudo tmutil disablelocal
This disables the “local snapshots” feature in Time Machine. After a moment or two, your Mac will automatically purge all the local snapshots from your startup disk, giving you back all that free space. Your Mac will never create local snapshots again, unless you run another command.
If you’d like to keep using local snapshots in the future, you can run the following command to re-enable this feature. Your Mac will resume creating local snapshots, starting over from scratch so they won’t immediately consume a lot of hard disk space:
sudo tmutil enablelocal
These backups are stored under the .MobileBackups folder under the root directory on your Mac’s boot drive. Because it begins with a . character, it’s normally hidden from the Finder and other Mac applications so you can’t see it. Don’t try to delete those files by hand — to purge Time Machine’s local snapshots, just use the above command.
Image Credit: Anders.Bachmann on Flickr