What’s difference between NSPhotoLibraryAddUsageDescription and NSPhotoLibraryUsageDescription?
Simple get from Apple Official Document Just click on above image for ZOOM and read it. For more information on: NSPhotoLibraryAddUsageDescription: If you want to save a photo/image to your Photo Library. For iOS11 and + NSPhotoLibraryUsageDescription: If you want to access your Photo Library. For iOS10 and +