watchOS 5.1.3 (build 16S535) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2019-01-22T18:12:22Z. The update package is 162.77 MB. This is a delta (partial) update that requires 5.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: bc8d54269aae07e812268f73a15a9e23187b668b.zip.