iOS 9.3.1 (build 13E238) is an official Apple over-the-air update for the iPhone 4s, released on 2016-03-31T16:54:31Z. The update package is 932.08 MB. This is a delta (partial) update that requires 8.0.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 973bf3e40a10c9a592897dcd7251b57a690c1144.zip.