watchOS 4.3 (build 15T5176c) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-02-07T18:10:25Z. The update package is 103.8 MB. This is a delta (partial) update that requires 4.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 2942089d32c24a253228ac5e6012950d3716faa9.zip.