watchOS 4.3 (build 15T5187e) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2018-02-21T18:11:23Z. The update package is 356.74 MB. This is a delta (partial) update that requires 4.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 7db2006d8c483fe05aada16fd3c1d6f22c2def42.zip.