watchOS 4.0 (build 15R5371a) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2017-08-28T16:53:17Z. The update package is 527.93 MB. This is a delta (partial) update that requires 3.2.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 61568aba5eca27d9934eecfa473601d4f21f01d0.zip.