watchOS 4.3.1 (build 15T5545b) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2018-04-16T17:04:00Z. The update package is 83.46 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: 76292a983c341876a4fa87c1262bbc5d3a0dd632.zip.