watchOS 5.0 (build 16R5357a) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2018-08-20T17:08:57Z. The update package is 193.01 MB. This is a delta (partial) update that requires 5.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d17b985585b3f593cf472303cc9c6aeedd044f4f.zip.