iPhone storage
How do I move everything from my iPhone storage to my iCloud storage
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There are things that can't be moved.
Usually Apple apps use the service as storage, like Photos and Files, for exemple. Photos app can be set to optimize local storage and then your original photos will be stored in iCloud and downloaded back when you click to open them. Everything that you place in Files can also be stored in iCloud Drive and will be managed by the iOS the same as Photos.
3rd party apps don't do that. They have their data stored on the device. They can do backups to iCloud, but only backups, still keeping the files on the phone.