iOS 9.2.1 (build 13D15) is an official Apple over-the-air update for the iPhone 6s, released on 2016-01-19T18:20:45Z. The update package is 34.58 MB. This is a delta (partial) update that requires 9.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 8f633ad9c2103c974ea556142069cdaf74ed5c9d.zip.