watchOS 5.0 (build 16R5357a) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2018-08-20T17:08:47Z. The update package is 605.32 MB. This is a delta (partial) update that requires 4.3.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6c725a6a7ab9d98087f6713c83090de1f9c7ad83.zip.