iOS 11.4 (build 15F79) is an official Apple over-the-air update for the iPhone 6, released on 2018-05-29T17:16:20Z. The update package is 687.32 MB. This is a delta (partial) update that requires 11.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 033692e64b6425c56a11d335f8c427aec8f77f16.zip.