From `NSHTTPURLResponse` documentation, I did not find a way to get the `HTTP` version `(i.e. "HTTP/1.1" or "HTTP/1.0")`. 

`HTTP` header fields are available through all Header Fields property, however the `HTTP` protocol version is not given inside the header fields as it is not an `HTTP` header. 

**Note:** init, `NSHTTPURLResponse` initializer 
`(initWithURL:statusCode:HTTPVersion:headerFields:)` does require the `HTTPVersion` as an input, so theoretically it may have been saved there. 

However, I couldn't find a property or method to get the `HTTPVersion` from a given response, for example a response returned from an NSURLSessionDataTask.