watchOS 5.0 (build 16R5283q) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2018-06-05T09:52:46Z. The update package is 570.26 MB. This is a delta (partial) update that requires 4.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: aa51e9659bed9e181925ef961becb08484dc878b.zip.