watchOS 5.3.9 (build 16U693) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2021-01-26T18:26:54Z. The update package is 454.87 MB. This is a delta (partial) update that requires 5.1.3 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: f70b2e364e360d9b88f94e6741a1b1af1e27d9a4.zip.