It s not my experience that nsurlsession is any slower than nsurlconnection is

Use nsurlsession instead;it replaces nsurlconnection and is far better

Nsurlsession is much more powerful tool than nsurlconnection

Nsurlconnection is a much older api introduced in os x 10.2;nsurlsession was introduced in os x 10.9 and has a more modern task- and block-based api

Using completionhandler -based methods of nsurlsession is much easier

Nsurlsession also provides nicer interfaces for requesting data using blocks in that it allows you to combine them with delegate methods for doing custom authentication handling redirect handling etc. whereas with nsurlconnection if you suddenly realized you needed to do those things you had to refactor your code to not use block-based callbacks

Nsurlconnection cannot help you there;nsurlsession has a facility for uploading files in the background outside of that time

Nsurlsession is newer than nsurlconnection if you are using swift language then you can use your own custom methods by using nsurlsession or you can use alamofire

A bit of history before nsurlsession came out a third party library afnetworking became the de facto standard for doing networking in objective c as it provided an easier and more convenient api than nsurlconnection which it was a wrapper around - i think these days it wraps nsurlsession instead