watchOS 5.1 (build 16R5584a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-10-15T17:10:09Z. The update package is 59.56 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: 12cffc31c585d7f451e90fc36eab3536dce8581f.zip.