watchOS 5.1 (build 16R591) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-10-30T17:21:36Z. The update package is 145.13 MB. This is a delta (partial) update that requires 5.0.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: fb6bd18f29c9bf430d989cf8d81ce6f9bde77199.zip.