watchOS 5.1 (build 16R6591) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-10-30T17:21:40Z. The update package is 81.61 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: 3367b34089921f4c9b22e6121fbecca2257b286f.zip.