iOS 9.3.1 (build 13E238) is an official Apple over-the-air update for the iPhone 5 (GSM), released on 2016-03-31T16:54:40Z. The update package is 223.02 MB. This is a delta (partial) update that requires 9.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 24d6ef3cbaca07b67b2a4825829f9bd88f7474cd.zip.