watchOS 4.3 (build 15T6212) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2018-03-29T17:09:32Z. The update package is 181.64 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: 30bc5c876166e733986c535597283eba26b663b7.zip.