watchOS 5.1.3 (build 16S535) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2019-01-22T18:10:55Z. The update package is 979.85 MB. This is a delta (partial) update that requires 3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 3c49b19c39f3fd9c5440bf3833ade5deb83f8f9e.zip.