watchOS 4.3 (build 15T212) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2018-03-29T17:07:31Z. The update package is 306.87 MB. This is a delta (partial) update that requires 4.2.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 7c2221dee6a9ac4f18d164b1d4022bc76ebcbc62.zip.