watchOS 5.0 (build 16R5357a) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2018-08-20T17:08:52Z. The update package is 610.16 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: 9955e5df1b6ee927bc332c1915062c916f6874f6.zip.