watchOS 4.3 (build 15T5212a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-03-16T20:09:44Z. The update package is 344.02 MB. This is a delta (partial) update that requires 4.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6f6006e31d6e4c24133751bfcf6680c39b1e1f0f.zip.