watchOS 4.3.1 (build 15T5565a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-05-07T17:23:44Z. The update package is 145.13 MB. This is a delta (partial) update that requires 4.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 00a7bea0bc68adc9c17c1eab2958aac1ce774829.zip.