watchOS 4.2.3 (build 15S6600b) is an official Apple over-the-air update for the Apple Watch (38mm), released on 2018-02-19T21:17:10Z. The update package is 55.12 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: 6970d1a53b8e702474ee2c8b32e0923bbfde303f.zip.