watchOS 5.1 (build 16R591) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2018-10-30T17:20:57Z. The update package is 748.54 MB. This is a delta (partial) update that requires 4.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 8cb842dc8634d87054bbe196d351995d4501d832.zip.