iOS 9.3 (build 13E237) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2016-03-28T16:52:42Z. The update package is 1.14 GB. This is a delta (partial) update that requires 8.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 08027c7ff349ecae92c844aed64c65f086b0fc7f.zip.