watchOS 6.0 (build 17R575) is an official Apple over-the-air update for the Apple Watch Series 4 (40mm, LTE), released on 2019-09-11T18:36:33Z. The update package is 708.44 MB. This is a delta (partial) update that requires 5.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6701becba5ded2f17530de8e2b4bcaa24c258479.zip.