watchOS 4.3 (build 15T5199f) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-03-06T18:08:36Z. The update package is 369.52 MB. This is a delta (partial) update that requires 4.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 4cb5fe0b59647a8872f8197ca8d8f9f27b798bd0.zip.