Change Devices preferences in iTunes on Mac

In the iTunes app on your Mac, use the Devices pane in iTunes preferences to view and delete device backups, choose syncing options and more.

To change these preferences, choose iTunes > Preferences, then click Devices.

Device backups				Displays a list of backups of devices that are synced with this computer. Encrypted backups are identified with a lock icon. Position the pointer over an item in the list to display the device’s serial number.
Delete Backup				Delete the selected backup. All backed up files are deleted and can’t be recovered.
Prevent iPods, iPhones and iPads from syncing automatically				Prevent devices from automatically syncing with this iTunes library when a device is connected. To sync a device, click the Sync button when the device is connected.
Forget All Remotes				Disconnect every iPod touch, iPhone and iPad paired with this iTunes library via the Remote app.

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iTunes User Guide