What is the MobileSync folder, and what is safe to delete?

Where it is

Press Windows+R and paste the line that matches how you installed Apple's software:

• Apple Devices, or iTunes from the Microsoft Store: %USERPROFILE%\Apple\MobileSync\Backup
• iTunes downloaded from Apple's website: %APPDATA%\Apple Computer\MobileSync\Backup

If both open, you have backups in both places. Each one counts against the same drive.

What is inside

One folder per device, named with a long string of letters and digits. That string is the phone's own identifier, so the same iPhone always writes to the same folder. A folder with a date and time added to the end of its name is an archived copy: iTunes saved it to the side so the next backup would not overwrite it.

Open a device folder and you will find a few hundred subfolders named 00 to ff, plus four files at the top: Info.plist, Manifest.plist, Manifest.db and Status.plist. The subfolders hold the data. Manifest.db is the index that says which scrambled file name is which file on the phone.

To tell the folders apart, open Info.plist in Notepad and search for Device Name and Last Backup Date. The text on the next line is the answer. It takes ten seconds per folder.

Why it gets so big

A backup copies most of what is on the device: messages with years of attachments, app data, and any photos not already in iCloud Photos. Nothing is shared between devices, so two phones means two complete copies.

Then the copies pile up. An archived backup is a whole second copy, not a list of changes. A phone you sold four years ago still has its folder. A 64GB iPad cannot fill a 500GB drive on its own. Several copies of it, next to two old phones, can.

What is safe to delete, and what each one costs

• A device you no longer own. Safe. You may lose the only copy of whatever was on it, so open Info.plist first and make sure it is the one you think it is.
• An archived copy. Safe, as long as a newer backup of the same device exists. You lose that moment in time, which only matters if something was deleted from the phone after it was made.
• The current backup of the phone you use. Safe for the phone. You lose the restore point until the next backup, and that next one starts from nothing and takes much longer. If the phone breaks or is lost in between, there is nothing on this PC to restore from.
• Files or numbered subfolders inside a backup. Not safe. The index still lists them, so a restore from that backup will fail, however much space it frees. Delete the whole device folder or none of it.
• The whole MobileSync folder. Every backup on this PC goes at once. iTunes or Apple Devices makes a new folder the next time it backs up a device.

How to delete one

Use Apple's own list where you can, because it shows the device name and date beside each backup. In Apple Devices, connect any iPhone or iPad, select it, open General, then Manage Backups. In iTunes, it is Edit, Preferences, Devices. Pick the backup and choose Delete.

Deleting the device folder in File Explorer does the same thing. Then empty the Recycle Bin; until you do, the space is not back.

If you want to keep the backups but not on drive C

Apple gives you no setting to move MobileSync. The common workaround is a folder link (a directory junction): close iTunes and Apple Devices, move the Backup folder to the top of drive D, then run this in Command Prompt, using the path from the top of this page:

mklink /J "%USERPROFILE%\Apple\MobileSync\Backup" "D:\Backup"

Apple's software then writes to drive D without knowing it. Apple does not support this, and if that drive is unplugged when a backup starts, the backup fails.

Getting the messages out first

Most people clearing MobileSync want the space back without losing years of texts. Deleting a backup does not touch the messages on the phone. But if the backup is the only place an old conversation survives, that conversation goes with it.

ScribeHold reads the iPhone or iPad over the USB cable, not this folder. It makes its own copy, in its own folder outside MobileSync, and keeps only messages, attachments and contacts. That makes it small, and it also means ScribeHold is not a backup: you cannot restore a phone from it. Keep one real backup somewhere.

Searching every message is free. Opening anything older than 90 days needs a paid plan; the pricing page has the numbers.

Where ScribeHold is the wrong answer

• You have a backup folder and no phone. ScribeHold reads the device, so a folder on its own is no use to it. A tool that opens existing backup files is.
• Encrypt Local Backup is on and staying on. ScribeHold does not support encrypted backups. That setting lives on the phone, so it applies to ScribeHold's copy too, and the run fails rather than handing you half the history.
• The messages are already gone from the phone. If iOS has erased them, reading the phone will not find them. An older backup in MobileSync might still hold them, which is one more reason to check before you delete it.

If you are doing this today

Open each device folder's Info.plist, delete the old phones and the archived copies you do not need, and leave the current backup alone. On a PC that has backed up more than one phone, that is often most of the space.

If you want the messages somewhere you can read them first, download ScribeHold for Windows and search before you decide. The limitations page lists everything it cannot do.