watchOS 5.3.1 (build 16U600) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2019-08-26T17:14:09Z. The update package is 856.03 MB. This is a delta (partial) update that requires 4.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d729c340a493023ad3d254021218dad874bc1ccf.zip.