watchOS 4.3.1 (build 15T5535b) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2018-04-02T17:13:06Z. The update package is 87.91 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: efff788380a4e9cfda1784d631516e555c954c94.zip.