watchOS 5.3 (build 16U6569) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2019-07-22T19:20:34Z. The update package is 147.1 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: 4cdfaac497eddbc84de58b191311921f59b116e7.zip.