watchOS 4.2 (build 15S102) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2017-12-05T18:00:53Z. The update package is 554.77 MB. This is a delta (partial) update that requires 3.2.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 7415486c5b6f4342dd2732c277a40a215dc038a5.zip.