iOS 9.3.1 (build 13E238) is an official Apple over-the-air update for the iPhone 6, released on 2016-03-31T16:55:19Z. The update package is 1.16 GB. This is a delta (partial) update that requires 8.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: cbf6f339b9a2dcb9f24bec9e03f7a4267104a534.zip.