watchOS 4.0 (build 15R5365a) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2017-08-22T16:58:55Z. The update package is 1.07 GB. This is a full OTA update that can be applied from any compatible base version. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: a700bea6fbf3477d3dd3a2acdd72b2996c90c697.zip.