iOS 9.3 (build 13E233) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2016-03-21T18:56:24Z. The update package is 1.14 GB. This is a delta (partial) update that requires 8.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: ab1aa499d780f6dd6afd4ceef954f6ec11560374.zip.