watchOS 4.2 (build 15S5100a) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2017-11-13T18:03:14Z. The update package is 176.4 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: 57de851188baed014ace9e952c78b37c499f370c.zip.