watchOS 4.2 (build 15S102) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2017-12-05T18:01:23Z. The update package is 200.83 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: 4fff9ac65dd14df1e20e44a437d63c908a4c1c23.zip.