watchOS 4.2.3 (build 15S600b) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2018-02-19T21:17:28Z. The update package is 618.68 MB. This is a delta (partial) update that requires 3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 30f9e3240ef59b182aa7b53680108f16a6e29f47.zip.