watchOS 5.3.9 (build 16U693) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2020-11-05T18:19:50Z. The update package is 52.43 MB. This is a delta (partial) update that requires 5.3.5 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: bc25b07d9cff7e07b9bee5a6ad17417f6dee2171.zip.