watchOS 4.3 (build 15T5209a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-03-12T20:07:49Z. The update package is 333.08 MB. This is a delta (partial) update that requires 4.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 957736ad8fc95447e2d91d23f5e819897ac07d92.zip.