iOS 9.2.1 (build 13D15) is an official Apple over-the-air update for the iPhone 6s, released on 2016-01-19T18:20:44Z. The update package is 1.43 GB. This is a delta (partial) update that requires 9.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 1ad1c85ee991e39a5587d14bf38f366f8f4b81bd.zip.