watchOS 4.3 (build 15T212) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2018-03-29T17:09:12Z. The update package is 374.73 MB. This is a delta (partial) update that requires 4.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: a09307ad256762245e6c4e66de629004438f1061.zip.