iOS 12.1.3 (build 16D39) is an official Apple over-the-air update for the iPhone 6s, released on 2019-01-22T18:10:35Z. The update package is 1.73 GB. This is a delta (partial) update that requires 10.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 08ad6f005e99d723f4df7406efb142b9f36180c1.zip.