watchOS 4.2.3 (build 15S600b) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2018-02-19T21:17:43Z. The update package is 181.14 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: 0f1f009cb1cd1b38b803be4eade948b9b58ac48f.zip.