Seems like there are two potential issues: Your cache is too small. Historically, it wouldn't cache if the item being cached exceeded 10% of the total cache size. You're checking the disk usage 0.5 seconds after the last request. That might be too soon for the cache to be written to persistent storage. Below I use a bigger cache and wait 10 seconds before final check of disk usage, and the cache w
![Why is NSURLSession don't use my configured NSURLCache?](https://cdn-ak-scissors.b.st-hatena.com/image/square/98d6f053a97a87156775f60757c60865d0f2c47d/height=288;version=1;width=512/https%3A%2F%2Fcdn.sstatic.net%2FSites%2Fstackoverflow%2FImg%2Fapple-touch-icon%402.png%3Fv%3D73d79a89bded)