iOS 12.1.3 (build 16D39) is an official Apple over-the-air update for the iPhone 6s, released on 2019-01-22T18:10:34Z. The update package is 1.73 GB. This is a delta (partial) update that requires 10.1.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 66a769230013901fa14f850c4da5bed08b998dac.zip.