watchOS 5.3 (build 16U5537b) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-05-28T17:13:02Z. The update package is 169.8 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: 00b2be87afd1d0c2bc043140d3e91ec661334d90.zip.