watchOS 5.1 (build 16R5577c) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-10-09T17:12:16Z. The update package is 405.81 MB. This is a delta (partial) update that requires 5.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 22eb2453526fcf1f8d03b626d95ecf004c5c76e0.zip.