watchOS 4.3.1 (build 15T6567) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2018-05-29T17:09:27Z. The update package is 86.63 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: 2c7d87a57b391685d67eae6d4232fce8cb834c3e.zip.