watchOS 5.1 (build 16R591) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2018-10-30T17:20:54Z. The update package is 977.05 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: 26e515f2c9b68dfee04ef987983c9463dd83424e.zip.