iCloud Backup Size Inconsistency

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iCloud Backup Size Inconsistency

Hi everyone, I transferred from my old iPhone 17 Pro (which had sound issues) to a new iPhone 17 Pro using the “Transfer from another iPhone” method, not from an iCloud backup. Both phones have the exact same specs and iOS versions. On my old iPhone, my iCloud backup size was 36.8 GB, but when I backed up the new iPhone it was 36.1 GB, even though everything was transferred directly. I don’t understand how the backup sizes can differ when nothing changed and the transfer was a full device to device copy. I also tried deleting the backup and creating a new one. Same issue.

The second issue is that the backup size doesn’t make sense at all. My new backup shows 36.1 GB, but when I look at the list of apps it backs up, just the first two apps already add up to ~36.5 GB. So the total backup size is somehow smaller than the combined size of only two apps, which obviously shouldn’t be possible. I deleted the entire backup, made a new one, restarted the phone and tried again, but the numbers stay the same.

Another strange thing is that the “Next Backup Size” shows 2.6 GB, but when I create a new backup, those 2.6 GB do not get added. The backup stays at 36.1 GB. I tracked it for a week, the backup size increases but the next backup size stays around 1.7 GB.

Are those some kind of iCloud or iOS bugs on the iPhone 17 Pro?

Posted on Nov 15, 2025 3:37 AM

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Answer 1

Top-ranking reply

zinacef

Level 10

88,720 points

Dec 4, 2025 3:32 PM in response to Online_Kritiker

The size discrepancy you are seeing is standard behavior rather than a defect, as a direct device-to-device transfer copies temporary cache files and system logs that a fresh iCloud backup efficiently excludes to save space. The reason your total backup size is smaller than the combined size of your apps is that iCloud deliberately ignores offline media downloads—such as saved Netflix movies or Spotify songs—backing up only the essential app data and settings instead of the massive content files you can re-download later.

Additionally, the "Next Backup Size" indicator is a notoriously unreliable estimate of incremental changes (deltas) rather than a precise total, so as long as the backup completes successfully, you can safely ignore these fluctuating numbers.

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