iOS 9.3 (build 13E234) is an official Apple over-the-air update for the iPhone 6s, released on 2016-03-21T18:56:37Z. The update package is 380.42 MB. This is a delta (partial) update that requires 9.0.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 9412634dd35352fa8e4711dc2dbc52f7f6743425.zip.