iOS 9.3 (build 13E237) is an official Apple over-the-air update for the iPhone 4s, released on 2016-03-28T16:52:17Z. The update package is 927.76 MB. This is a delta (partial) update that requires 8.1.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 422aca77ef4455f10835e949735f6a509162c553.zip.