Short answer: neither one is a complete copy of your phone, and they do not contain the same things. An iCloud backup deliberately skips anything already stored in iCloud. A computer backup is a wider local snapshot — but it only includes saved passwords and Health data if you turn encryption on first.
What each one actually contains
| iCloud backup | Computer backup | |
|---|---|---|
| App data and device settings | Yes | Yes |
| Home screen and app layout | Yes | Yes |
| Messages (SMS and iMessage) | Yes, unless iCloud Messages is on | Yes |
| Photos and videos | Only if iCloud Photos is off | Only if iCloud Photos is off |
| Health data | Yes, if Health sync is on | Only with encryption |
| Saved passwords | No — those live in iCloud Keychain | Only with encryption |
| The apps themselves | No | No |
| Apple Pay cards | No | No |
| Bluetooth pairings | No | No |
The rows that say "No" all follow one rule: a backup covers data that lives on the device, and skips anything that can be fetched again or already lives somewhere else. Apps come back from the App Store. Apple Pay cards are re-issued by the bank. Bluetooth pairings are re-established by pairing. None of those need to be in a backup, so none of them are.
That rule also explains the single most common misunderstanding about iCloud: if iCloud Photos is switched on, your photos are in iCloud, and the backup does not contain them. If it is switched off, the camera roll is part of the backup — and it is usually the largest thing in it.
Why the backup looks alarmingly small
The gap between "180GB used" and "6GB backup" is not data loss. A backup leaves out:
- iOS itself. The system is not something you own a copy of; it is installed fresh.
- The apps. Only their data is backed up. The binaries re-download.
- Anything re-downloadable. Offline Apple Music, downloaded podcasts, offline maps, and similar content are deliberately excluded.
- Anything already in iCloud, in the case of an iCloud backup — Photos (when iCloud Photos is on), Contacts, Calendars, Notes, Reminders, and Messages if iCloud Messages is enabled.
What is left is the part that genuinely cannot be reconstructed: your settings, your app data, your messages, your call history, and your photos if they are not already in iCloud. For most people that is a few gigabytes, not a few hundred.
A small backup is a healthy backup. The number to worry about is a timestamp that stopped moving, not a size that looks too low.
How to verify a backup actually ran
This is the part almost everyone skips, and it is the only part that matters.
- iCloud: Settings → your name → iCloud → iCloud Backup → read Last Successful Backup. Check the date, not the switch.
- Computer: open Finder, select the device, and read Last Backup to This Computer. "Manage Backups" lists every one that exists.
- Know when automatic backups run: iCloud backs up only when the phone is on Wi-Fi, plugged in, and locked. A phone that is never left charging overnight can go a long time between backups without ever displaying an error.
The trap: a backup that silently stopped working three months ago looks exactly like a working one. Same settings screen, same switch in the same position, no warning anywhere. The timestamp is the only honest signal you get, so make a habit of reading it. If it says "Backup Failed", you do not currently have a backup — you have the intention of one.
One more thing worth knowing before you need it: iCloud keeps one backup per device, the newest one. A failed attempt does not delete the previous backup, but you also cannot go back to an older one. There is no history to choose from.
What people lose when they restore
The restore finishes, everything looks right, and then a week later something is missing. The usual list:
- Chat history in apps that keep messages on their own servers. These apps are not part of the system backup in the way people assume. They need their own built-in migration, and it has to be done from the old phone while it still works.
- Authenticator codes with no cloud sync. These exist only on the old device. Set them up on the new phone before erasing the old one, or you can lock yourself out of your own accounts.
- Apple Pay cards and banking apps. Cards are removed on restore and must be re-added, and bank apps usually require re-enrolment.
- Bluetooth pairings. Car, watch, headphones — all need pairing again.
- eSIM. Depending on the carrier, the plan may need re-activation or a transfer request.
- Health data and saved passwords, if your only backup was an unencrypted computer backup.
None of these are reasons to avoid restoring. They are reasons to check the list before you erase the old phone, while you still can.