watchOS 4.3 (build 15T212) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2018-03-29T17:07:22Z. The update package is 668.2 MB. This is a delta (partial) update that requires 3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: a252bf6e4c0e281e11013bc30614d4d948af24ac.zip.