iOS 12.1.3 (build 16D39) is an official Apple over-the-air update for the iPhone 6s, released on 2019-01-22T18:10:46Z. The update package is 1.38 GB. This is a delta (partial) update that requires 11.0.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 46ddc40010357a387236c2f3b1e4389138ed8bc0.zip.