watchOS 5.0 (build 16R364) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2018-09-12T19:18:40Z. The update package is 971.05 MB. This is a delta (partial) update that requires 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: 5ea93f9d39f94ca9d455692c912d423aebe6a5bf.zip.