watchOS 4.3 (build 15T5165e) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2018-01-25T18:03:58Z. The update package is 297.74 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: 4c2be46db3dc7785b668f674306dab21f32fcb79.zip.