If your iPhone says “last iCloud backup could not be completed,” the alert does not identify one specific fault. Check your Wi-Fi connection, available iOS updates, another Wi-Fi network, and whether your iCloud storage can fit the next backup. Apple recommends these checks in its iCloud backup troubleshooting guidance.
Check the connection your iPhone is using
First confirm that the iPhone is connected to Wi-Fi: open Settings > Wi-Fi and check the connection. If the backup still will not complete, try it on a different Wi-Fi network. Apple specifically recommends testing another network, which can help distinguish a problem with the current connection from other possible causes.
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Check for an iOS update
Open Settings > General > Software Update. If an update is available, install it, then try the backup again. The alert itself does not establish that outdated software is the cause; this is one of Apple’s recommended checks.
Compare iCloud storage with the next backup size
Go to Settings > [your name] > iCloud to check your iCloud storage usage. Then open Storage or Manage Account Storage > Backups, select this iPhone, and check Next Backup Size. Apple notes that the estimate may take a few minutes to appear.
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If the next backup needs more space than is available, Apple suggests reducing the information included in the backup or upgrading your iCloud+ plan. Check the estimate before changing storage or backup settings; the alert alone does not show whether space is the problem.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Try the checks without assuming a single cause
- Wi-Fi: Confirm the connection in Settings, then test a different network.
- Software: Check for and install an available update.
- Storage: Compare available iCloud space with the iPhone’s Next Backup Size estimate.
These are separate troubleshooting avenues, not a guaranteed diagnosis. Apple’s guidance for this message does not identify a physical product as a fix.
Quick Recap
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