watchOS 4.3.1 (build 15T6567) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-05-29T17:09:46Z. The update package is 99.15 MB. This is a delta (partial) update that requires 4.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 4120dc66b5217de8f905dd88663731b92a6a41a7.zip.