watchOS 4.3.1 (build 15T5567a) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2018-05-14T17:13:44Z. The update package is 96.3 MB. This is a delta (partial) update that requires 4.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 25b0bcce41a3e2f9d740142cf215e3d88bc92675.zip.