watchOS 4.3.1 (build 15T5567a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-05-14T17:14:24Z. The update package is 333.1 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: d4936c77b9cee5fab6b1aa0505f3a9f39b6a9edf.zip.