“Other” Storage on Your iPhone and iPad Explained
Christian Zibreg (via John Gordon):
Say you then launch Videos and stream a five-gigabyte movie that was purchased on the iTunes Store.
The reported storage usage for the Videos app in Settings won’t increase at all.
But if you glance at the amount of free device storage reported in Settings, you’ll notice it has dropped by five gigabytes due to that streamed video being cached automatically by iOS, thereby taking up five gigabytes of ‘Other’ storage.
Because the amount of device storage wasted on the ‘Other’ category cannot be directly checked out in iOS, less experienced users may be left scratching their head, puzzled as to why their reported free storage isn’t higher.
[…]
The 291-megabyte difference between the 856MB seen in desktop iTunes and 565MB reported by my iPhone is actually caches for the songs I had streamed via Apple Music.
[…]
People who use iCloud Photo Library with the ‘Optimize iPhone Storage’ option may observe a similar discrepancy in the ‘Photos’ storage section between iTunes and iOS Settings, due to large caches of photos in device-optimized resolution.
