watchOS 4.3.1 (build 15T567) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-05-29T17:09:44Z. The update package is 340.03 MB. This is a delta (partial) update that requires 4.2.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: de10eda71e75d3fa956fbf8d723a350240981496.zip.