watchOS 5.0 (build 16R5357a) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2018-08-20T17:08:45Z. The update package is 608.95 MB. This is a delta (partial) update that requires 4.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 8c4a4737773b6cc77daa0bdaae7fb757872dc010.zip.