watchOS 5.3 (build 16U569) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2019-07-22T19:16:07Z. The update package is 906.72 MB. This is a delta (partial) update that requires 4.0.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 397bfcea1691d18fa43b852141a56ae125a9bfb2.zip.