How To Force Optimising of iCloud Photo’s Local Storage Ise?

How much storage are your photos using in iCloud? Even with "Optimised storage" enabled, your photos and videos will need a lot of storage on the iPhone for the optimised version. It depends on the file format of the originals how much storage can be saved by "Optimise iPhone Storage", but you should expect that the optimised versions will use at least 10% to 20% of the storage used in iCloud. For example, if you have 100GB of photos and videos in iCloud Photos, they will probably still use at least 10GB locally on the iPhone. You cannot remove the photos completely from the iPhone, unless you delete them, but then they will be deleted from iCloud as well. The optimisation is fully automatic. You cannot control it yourself. But the iPhone storage may always appear to be full, because Photos will try to keep recently downloaded photos stored locally, until another app needs the storage. Then the photos should be purged again automatically to free the storage for apps that need it.