watchOS 5.1 (build 16R591) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-10-30T17:21:35Z. The update package is 748.26 MB. This is a delta (partial) update that requires 4.3.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: a07af45f4bd59a88f244adcfe6f0718438671d1d.zip.