iOS 12.0 (build 16A5354b) is an official Apple over-the-air update for the iPhone 6s, released on 2018-08-13T17:03:58Z. The update package is 1.21 GB. This is a delta (partial) update that requires 11.4.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: ace21fcd0d191c5300bcd5af5884f0a892fd1bcc.zip.