iOS 12.1.3 (build 16D40) is an official Apple over-the-air update for the iPhone XR, released on 2019-01-22T18:15:11Z. The update package is 318.06 MB. This is a delta (partial) update that requires 12.1.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c1947eae83b2b9faa7ddcaa83a272ca286b5d211.zip.