iOS 11.4 (build 15F5079a) is an official Apple over-the-air update for the iPhone 6s, released on 2018-05-17T17:02:30Z. The update package is 276.2 MB. This is a delta (partial) update that requires 11.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d6cd7a6e7adaae99fd14b5dd190efa3c23a1b947.zip.