watchOS 5.3.1 (build 16U6600) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2019-08-26T17:14:29Z. The update package is 99.59 MB. This is a delta (partial) update that requires 5.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 534829734436922b72c15574a4d4b9f232a5c44f.zip.