How iCloud Backup works
iCloud helps keep your data safe in two main ways: syncing and backing up. For example, if you’re using iCloud Photos, iCloud Drive or Notes, your information will be synced to the cloud automatically and kept up to date across all of your devices whenever you make a change.
Any data on your device that isn’t synced regularly will be stored in your iCloud Backup. With Backup turned on, iCloud takes periodic snapshots of this data to make sure it’s easy to restore any time you get a new device.
Between syncing and backing up, all of your data is kept safe in the cloud.
What iCloud Backup includes
Your iPhone and iPad backups include all the information and settings stored on your device that don't already sync to iCloud.
Device settings, Home Screen layout and app organisation
When you restore from an iCloud backup, things like your device settings, your Home Screen layout and app organisation will also be restored.
Other on-device information
Any purchased Ringtones and your Visual Voicemail password (which requires the SIM card that was in use during the backup) will also be included in your iCloud Backup.
Apple Watch backups
Your Apple Watch backup will be included in the backup of your iPhone or iPad.
Photos, videos, messages and app data
If you don’t use services such as Messages in iCloud or iCloud Photos, the information below will be stored in your iCloud Backup to ensure it’s also protected.
iMessage, text (SMS) and MMS messages
If you haven’t turned on Messages in iCloud, your messages will be included in iCloud Backup. If you use Messages in iCloud, your messages will be synced to iCloud automatically so they’re not included in your daily backup.
Photos and videos on your iPhone or iPad
If you haven’t turned on iCloud Photos, iCloud Backup may include photos and videos in your Photos or Camera Roll, as well as face information from the People & Pets album. When you use iCloud Photos, your photos, videos and face information automatically sync to iCloud so they aren’t included in your daily backup.
iCloud Backup includes app data for the apps you’ve downloaded on your device. This includes data for third-party social media apps, games and messaging apps, as well as apps from Apple that don’t sync with iCloud.
If the app uses iCloud Drive to store data, that information will be stored in iCloud instead of your iCloud Backup.
How to manage your iCloud backups
If you want to reduce the size of your iCloud Backup, you can stop backing up apps that you don't use any more, or delete old iCloud backups.