watchOS 5.3 (build 16U5569a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2019-07-16T17:14:37Z. The update package is 153.82 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: 40dad3ab989471636f78c634e5b4d35b16933cd9.zip.