watchOS 5.0 (build 16R5349a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2018-08-13T17:06:49Z. The update package is 534.2 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: 2021333e84800c29f968a9b6b575506bc39857c5.zip.