On iPhone OS, Apple did remove on-disk cache support for unknown reason. Some will say it's to save flash-drive life, others will arg it's to save disk capacity. As it is explained in the NSURLCacheStoragePolicy, the NSURLCacheStorageAllowed constant is always treated as NSURLCacheStorageAllowedInMemoryOnly and there is no way to force it back, the code is certainly gone on this platform. For whatever reason Apple removed this feature, you may be interested by having on-disk HTTP request caching in your application. SDURLCache gives back this feature to this iPhone OS for you.To use it, you just have create an instance, replace the default shared NSURLCache with it and that's it, you instantly give on-disk HTTP request caching capability to your application.