watchOS 6.3 (build 17U216) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2021-01-26T18:27:11Z. The update package is 580.75 MB. This is a delta (partial) update that requires 6.0.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: da48eea21b5abbae8336731a55cae9df023e4676.zip.