Why do I get the alert iPhone storage full on iOS 15? Is iPhone storage full message a bug?
Some iPhone owners have received an alert that they are running out of iPhone storage after updating to iOS 15.0. This is despite the fact that plenty of free space exists on the device.
This is no cause for alarm, because it does not affect the available storage on your device. However, it's possible the false message is a bug in the initial iOS 15 release. Apple will likely release a fix for this issue.The alert can be safely ignored.
For more details see AppleInsider.