watchOS 5.1 (build 16R591) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2018-10-30T17:21:18Z. The update package is 793.38 MB. This is a delta (partial) update that requires 4.2.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 29bff92bb446f6ea4bde4248548dbabea2ba5594.zip.