watchOS 4.3 (build 15T5165e) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm), released on 2018-01-25T18:05:03Z. The update package is 311.21 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: 3a08aa20fe8869d827824b66d1e31f0a2781988a.zip.