watchOS 4.0 (build 15R5372) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2017-09-12T19:05:17Z. The update package is 122.77 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: a76623a0e123d714b782128e451eda43bf3b388c.zip.