I just updated the iPhone to iOS 17.3. Problem remains unchanged. Is there any way to downgrade to 17.1?

Is the -valueForHTTPHeaderField: method not working for you? I tried that but Xcode didn't allow it, as NSURLSessionDownloadTask.response is a NSURLResponse object not a NSHTTPURLResponse object (which responds to -valueForHTTPHeaderField:) . However, I did cast the types and got it work work: NSDictionary *responseHeaders = ((NSHTTPURLResponse *)downloadTask.response).allHeaderFields; So that does work, thank you! But the file being downloaded is a .gz file. Is there a way in iOS to uncompress it programmatically?

I guess it would it make sense to: Deliver the app, but without the data files in the main bundle Have the user download the files upon first run of the app into ~/Documents Then the user could update at any time by downloading new data files.

Okay, I found the files in: /private/var/containers/Bundle/Application/26FA4220-0E34-43EF-AC23-0F46CABF906E/.app/dataset1.dat And I understand now that such "project" files don't go into the ../Documents folder. Q: Can my app modify the file contents in the main bundle? Or would it have to copy the file from the main bundle into the sandbox and then modify/update it?