watchOS 4.2 (build 15S6102) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2017-12-05T18:02:09Z. The update package is 55.64 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: c9cd100535903b08945f18b4ac4f6de26b5e6bfd.zip.