watchOS 4.0 (build 15R5365a) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2017-08-22T16:58:30Z. The update package is 39.44 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: f589391f070598f27062c22edaff912f8f12f2e6.zip.