Is It Safe to Delete Old iPhone Backups on Your Mac?

Yes, but read this firstDiskmack safety tier: Caution

~/Library/Application Support/MobileSync/Backup

Yes, you can delete old iPhone backups on your Mac, and it is often the single biggest chunk of space you can reclaim in one move. The catch: a deleted backup does not come back, so you need to be sure nothing in it still matters. Delete through Finder's Manage Backups screen or System Settings rather than dragging folders to the Trash, and your other backups stay safe.

What it is

Every time you back up an iPhone or iPad to your Mac through Finder (or iTunes on older systems), the backup is written to ~/Library/Application Support/MobileSync/Backup. Each device gets its own subfolder named with a long string of letters and numbers, which is why the contents look like gibberish when you open the folder. Inside each one is a near-complete snapshot of that device: messages, app data, settings, camera roll photos that were not in iCloud, and, for encrypted backups, Health and keychain data too.

These backups get big because they hold nearly all of your personal data. Apps themselves are skipped (a restore re-downloads them from the App Store), but their data, your message history with attachments, and any photos not in iCloud are all in there, so a backup from a phone with a full camera roll is not far off the phone's used storage. A single backup often runs several gigabytes and can reach tens of gigabytes on a heavily used device. The folder grows quietly over the years: every iPhone and iPad you have ever backed up to this Mac may have left one behind, including devices you traded in or handed down long ago. Finder normally updates one backup per device in place, but multiple devices and archived backups stack up.

Is it safe to delete?

Deleting a backup is safe in the sense that it cannot harm your Mac or the device itself. The risk is data loss: a backup is the only copy of whatever was on that device at that moment. If you delete the last backup of an iPhone you no longer own, the messages and photos inside it are gone permanently. So check before you delete. Open the backup list, look at the device names and dates, and keep anything from a device you might still need to restore.

Good candidates for deletion: backups of devices you have since wiped and sold, backups older than your current one for the same device, and backups of devices that also back up to iCloud. If you are unsure about one, copy its subfolder to an external drive first, then delete the original. Diskmack identifies this folder automatically and removes backups the safe way. Whatever you do, use the official interface instead of trashing subfolders by hand; the folders are named by device identifier, not device name, so it is very easy to trash the wrong one.

How to check its size

In Finder: In Finder, choose Go > Go to Folder (Shift-Command-G), paste ~/Library/Application Support/MobileSync/Backup and press Return. Select the Backup folder and press Command-I to see its total size. Each subfolder with a long hexadecimal name is one device backup.

In Terminal:

du -sh ~/Library/'Application Support'/MobileSync/Backup

The ~ expands to your home folder; the quotes handle the space in Application Support.

How to clean it

Open System Settings, click General, then Storage.
Wait for the storage list to load, then click the info button next to iOS Files. Every local device backup appears with its device name and size.
Select a backup you no longer need and click Delete, then confirm. Repeat for each old backup.
If a device is plugged in, you can also select it in the Finder sidebar, click Manage Backups under the General tab, select a backup, and click Delete Backup.
To archive instead of delete, first copy the backup's subfolder from ~/Library/Application Support/MobileSync/Backup to an external drive, then delete the original through the steps above.

Deleting a local backup does not touch your iCloud backups and does not affect the device itself. It only removes the copy stored on this Mac.

Will it come back?

The folder does not refill on its own. Deleted backups stay deleted, and nothing regenerates them in the background. It grows again only when you back up a device to this Mac, at which point Finder writes a fresh backup that can be tens of gigabytes on its own. If you back up your iPhone to this Mac regularly, the next backup will take that space right back; that is the folder doing its job. If you moved your backups to iCloud, the folder should stay empty.

Common questions

Will deleting local backups affect my iCloud backups?

No. iCloud backups live on Apple's servers and are managed from the device under Settings > [your name] > iCloud > iCloud Backup. The MobileSync folder only holds backups made directly to this Mac. Deleting one has no effect on the other.

How do I know which backup belongs to which device?

Don't try to decode the folder names; each one is the device's unique identifier, not anything readable. Use System Settings > General > Storage > iOS Files, or Finder's Manage Backups screen. Both list backups by device name, and Manage Backups shows the date of each backup too. Right-clicking a backup there also offers Show in Finder if you want to see the underlying folder.

Can I move iPhone backups to an external drive instead of deleting them?

Yes. Copy the device's subfolder from ~/Library/Application Support/MobileSync/Backup to an external drive, verify the copy completed, then delete the original through Manage Backups. To restore from it later, copy it back into the same folder first. Some people redirect the folder with a symlink so future backups land on the external drive, but that setup breaks if the drive is unplugged during a backup, so treat it as an advanced option.

Why is one backup 30 GB or more?

A backup contains most of the data stored on the device: photos and videos not offloaded to iCloud, message history with attachments, and app data. A phone with a full camera roll produces a backup nearly as large as its used storage. Turning on iCloud Photos shrinks future local backups considerably.