iOS 11.4 (build 15F79) is an official Apple over-the-air update for the iPhone 6s, released on 2018-05-29T17:16:31Z. The update package is 268.04 MB. This is a delta (partial) update that requires 11.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 53e0e62888d9301374f1f39b71bb515bfd76f4b9.zip.