watchOS 4.3 (build 15T5212a) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2018-03-16T20:08:57Z. The update package is 345.4 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: 059ba998c6fdf6bbb96138a15296358ea522ccc8.zip.