watchOS 4.0 (build 15R5365a) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2017-08-22T16:58:41Z. The update package is 1.08 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: 4b2eba0f23c55029e7195fea585958ae150408c1.zip.