iOS 9.3 (build 13E233) is an official Apple over-the-air update for the iPhone 4s, released on 2016-03-21T18:56:12Z. The update package is 254.46 MB. This is a delta (partial) update that requires 9.0.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 62f1f3b3b0c1ff4e5c07266d3611c6d70f9513c4.zip.