watchOS 5.3 (build 16U5566a) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2019-07-09T17:20:24Z. The update package is 214.52 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: ea945d6654517b5be4897a53df9053d919b41d6c.zip.