watchOS 4.2 (build 15S5102) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2017-12-05T18:02:02Z. The update package is 55.66 MB. This is a delta (partial) update that requires 4.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6dbd55c883c4c909d28693030d7e6a71dce4c85e.zip.