watchOS 5.3 (build 16U5558b) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-06-24T17:25:35Z. The update package is 118.15 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: 2c75c52e6f1cd9c51061403e3414416087939caa.zip.