iCloud
Also known as: what is iCloud, iCloud storage, Apple cloud
iCloud is Apple’s cloud service for storing photos, files, backups, and app data across your devices. Every Apple ID gets 5 GB free; paid iCloud+ tiers add more. iCloud storage is separate from the physical storage on your iPhone.
- 5 GB free per Apple ID; iCloud+ adds more
- Separate from your iPhone’s physical storage
- Holds backups, iCloud Photos, Drive, and Messages
iCloud storage vs device storage
These are two different things people constantly confuse. Device storage is the fixed space inside your iPhone (for example, 128 GB). iCloud storage is online space (5 GB free by default) used for backups, iCloud Photos, iCloud Drive, and Messages in iCloud.
Your iPhone can be full while iCloud has room, or the reverse. Buying more iCloud does not add space to the phone itself — though features like Optimize iPhone Storage use iCloud to keep smaller copies on the device.
What fills iCloud
The usual culprits are iCloud Photos, the device backup, and large Messages attachments. You manage it in Settings > [your name] > iCloud > Manage Account Storage.