watchOS 5.3.1 (build 16U600) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-08-26T17:16:49Z. The update package is 207.5 MB. This is a delta (partial) update that requires 5.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 5cc1e3b103c54faedfb608791e10b94bf5b669e5.zip.