iOS 10.3.1 (build 14E304) is an official Apple over-the-air update for the iPhone 6, released on 2017-04-03T17:00:34Z. The update package is 756.85 MB. This is a delta (partial) update that requires 10.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 58d8fdb4694770c57ed053a2d640766fdbb78dbc.zip.