watchOS 5.0 (build 16R364) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2018-09-12T19:18:47Z. The update package is 727.98 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: 589a10402536dd73365da334f13679c30991df5b.zip.