Some iPhone users have reported that they can't update to the latest iOS version since there is not enough space on their iPhone. In particular, older iPhone models might be affected.
The device manufacturer provides some advice, e.g., see these links:
@dsarkar
I think in the Apple support article, the second point (updating via iTunes) is from a high value.
AFAIK iTunes downloads all files on the disk from the PC/Mac and thus this method doesn't need any free space on the phone.
The only negative thing here is that probably not so many normal users have iTunes installed on their Windows machine.
Macs are different since iTunes is better integrated into the OS there.
You can also offload (thank you @Ein-Tim ) some apps, update the os and download the app again. The user data won't be lost. You'll also get a message from the os to do so, if you don't have enough free space.
@jucktnich
It's called "Offload". More infos here: https://support.apple.com/en-us/HT203097
Most helpful comment
You can also offload (thank you @Ein-Tim ) some apps, update the os and download the app again. The user data won't be lost. You'll also get a message from the os to do so, if you don't have enough free space.