Turning it on and running one now
Settings → your name → iCloud → iCloud Backup. Turn on Back Up This iPhone, and tap Back Up Now to run one immediately rather than waiting for the overnight schedule.
Automatic backups run when the iPhone is locked, connected to power and on Wi-Fi. On current iOS they can also run over cellular if you enable that on the same screen, though on a capped plan that is worth leaving off.
What an iCloud backup includes — and what it doesn't
It covers app data, device settings, the Home screen layout, Messages, ringtones, purchase history and photos if iCloud Photos is off. It restores an iPhone to the state it was in, which is the point.
It does not include anything already synced separately. Photos, Contacts, Calendars, Notes and Mail live in iCloud in their own right when their sync switches are on, so they are not duplicated into the backup. Our guide to backup contents covers the full picture.
The 5 GB problem
Apple's free tier is 5 GB, which has not changed in many years and is not enough to back up a modern iPhone. The usual symptom is not an error but silence: backups quietly stop succeeding and nobody notices until they need one.
Settings → your name → iCloud → iCloud Backup shows the date of the last successful backup. If it is weeks old, storage is almost certainly why. Our iCloud storage guide covers freeing space or upgrading.
Check that it actually worked
The last-backup date on the iCloud Backup screen is the only thing worth trusting. A backup that says it is in progress and never completes is a common failure mode, usually caused by the storage limit or by a Wi-Fi network that drops the connection.
Make it a habit to glance at that date before anything significant — an update, a repair, a trip. It takes five seconds and it is the difference between having a backup and assuming you do.
Reducing what it backs up
Under Settings → your name → iCloud → Manage Account Storage → Backups → this iPhone, every app is listed with the size of its backup data and a switch. Turning off an app that stores gigabytes you do not care about — a game, a downloaded map cache — shrinks the backup considerably.
Be deliberate about it. Turning off an app means its data is not in the backup, so a restore will bring the app back empty.
When iCloud is not the right backup
An iCloud backup cannot be restored onto an older version of iOS. If you are about to install something you might want to reverse — a beta, or a major release you are unsure about — you need a backup made on a computer instead, taken before you update.
That is the one scenario where iCloud is not enough. Our computer backup guide covers making one, and our pre-beta guide explains why the distinction matters.
Frequently Asked Questions
How do I back up my iPhone to iCloud?
Settings → your name → iCloud → iCloud Backup, turn on Back Up This iPhone, then tap Back Up Now.
Is 5 GB of iCloud enough to back up an iPhone?
Rarely. The free tier has not changed in years and most modern iPhones need more. Backups fail silently when it runs out.
Does an iCloud backup include my photos?
Only if iCloud Photos is off. With it on, photos live in iCloud separately and are not duplicated into the backup.
How do I know my backup worked?
The iCloud Backup screen shows the date of the last successful backup. That date is the only reliable confirmation.