watchOS 5.0 (build 16R364) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2018-09-12T19:18:56Z. The update package is 773.27 MB. This is a delta (partial) update that requires 4.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: a9d2326aa0e8fac5aa482ec6da9c36f5d15e8538.zip.