watchOS 5.3 (build 16U5545c) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2019-06-11T17:14:11Z. The update package is 154.6 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: bc4c57426c54f82c49d3bd60574e85ff38aafa44.zip.