watchOS 4.3 (build 15T212) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-03-29T17:09:39Z. The update package is 332 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: 3d11211f96ca99a67d04601b48e511cdf1f73c7d.zip.