watchOS 5.3 (build 16U5569a) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2019-07-16T17:15:05Z. The update package is 117.43 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: 64179f8fc803e3923a442c891602871eb88336ef.zip.