watchOS 4.3 (build 15T212) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2018-03-29T17:09:28Z. The update package is 362.35 MB. This is a delta (partial) update that requires 4.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c486c7b78b3b37f8a4306a036352c76e5ce85694.zip.