watchOS 5.3.3 (build 16U620) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2019-10-29T17:09:29Z. The update package is 50.72 MB. This is a delta (partial) update that requires 5.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d1a8fe84f484204f74a6b79084c2950ff6b3e4c8.zip.