[paws]

Apple introduced App Transport Security[1] with iOS 9. The setting is configured in your app's Info.plist[2].

[1] https://developer.apple.com/library/content/releasenotes/Gen...

[2] https://stackoverflow.com/a/48089038/2044952

[tzahola]

Yep. App Transport Security mandates that you have to explicitly whitelist the domains [0] which you want to access via plain http. This however, has nothing to do with certificate pinning, which the OP was mentioning.

[0] Of course you can use the blanket NSAllowsArbitraryLoads to allow plain HTTP everywhere.