watchOS 4.3 (build 15T5176c) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-02-07T18:10:24Z. The update package is 313.27 MB. This is a delta (partial) update that requires 4.2.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 382f55077984094d4441824a9e4ea0562ba0cd54.zip.