iOS 9.9.12.1 (build 16B5089b) is an official Apple over-the-air update for the iPhone 6s, released on 2018-10-22T17:02:07Z. The update package is 2.14 GB. This is a full OTA update that can be applied from any compatible base version. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 19cfd90dc70acfead2ffe6dd8b66cde13ac42e8b.zip.