watchOS 4.3.1 (build 15T5567a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-05-14T17:14:27Z. The update package is 46.52 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: d5ebd11fed416e94a57fa6461bf11460020fab2e.zip.