watchOS 4.0 (build 15R5372) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2017-09-12T19:05:13Z. The update package is 71.59 MB. This is a delta (partial) update that requires 4.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d856790f4b225ca95cf24f2a4dcf74ee1e28b627.zip.