watchOS 4.3.1 (build 15T567) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm), released on 2018-05-29T17:09:51Z. The update package is 339.59 MB. This is a delta (partial) update that requires 4.2.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: fff8048d4141416aa5fcf5cd30360634c0ee5096.zip.