iOS 9.1 (build 13B143) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2015-10-21T17:16:03Z. The update package is 1.09 GB. This is a delta (partial) update that requires 8.1.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 4883a7d89123658b642e8aa011815e6fe93af541.zip.