When the iPhone is backed up to a computer, the backup files are stored in a backup directory, which exists as a 40-character hexadecimal string and corresponds to the Unique Device Identifier (UDID) of the device. The newest devices have changed the UDID format—now it's a 24-character string, so their backups are named accordingly. The backup process may take a considerable amount of time, depending on the size of the data stored on the iPhone during the first backup. The location of the backup directory in which your backup data is stored depends on the computer's operating system. The following table displays a list of the common operating systems and the default locations of the iTunes backup directory:

During the first sync, iTunes creates a backup directory and takes a complete backup of the device. Currently, on subsequent syncs, iTunes only backs up the files that are modified on the device and updates the existing backup directory. This has not always been true since, in the past, a new backup was created every time the iOS device was backed up. Also, when a device is updated or restored, iTunes automatically initiates a backup and takes a differential backup. A differential backup has the same name as the backup directory but is appended with a dash (-), the International Organization for Standardization (ISO) date of the backup, a dash (-), and the time in a 24-hour format with seconds ([UDID]+ '-' + [Date]+'-'+[Time stamp]).

The iTunes backup may make a copy of everything on the device, including contacts, Short Message Service (SMS) messages, photos, calendars, music, call logs, configuration files, documents, the keychain, network settings, offline web application cache, bookmarks, cookies, application data (if selected), and more. For example, emails and passwords will not be extracted if the backup is not encrypted. The backup also contains device details, such as the serial number, UDID, Subscriber Identification Module (SIM) details, and phone number. This information can also be used to prove a relationship between the backup and the mobile device.

The backup directory contains four standard files, along with the individual files (up to iOS 9) or folders (iOS 10 and newer). Up to iOS 9, these four files were info.plist, manifest.plist, status.plist, and manifest.mbdb, but starting from iOS 10, we have the following standard files:

• info.plist
• manifest.plist
• status.plist
• manifest.db

These files store details about the backup and the device from which it was derived.