watchOS 5.3.1 (build 16U6600) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-08-26T17:16:56Z. The update package is 95.63 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: 8b86f0d8027037451ff3aee7d0d5e63e59eebc38.zip.