watchOS 4.3 (build 15T212) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2018-03-29T17:09:27Z. The update package is 400.46 MB. This is a delta (partial) update that requires 4.0.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 655f047c01a1f4b78e4eea7162a6417f793e3be1.zip.