watchOS 6.3 (build 17U216) is an official Apple over-the-air update for the Apple Watch Series 5 (44mm, LTE), released on 2021-01-26T18:27:29Z. The update package is 446 MB. This is a delta (partial) update that requires 6.1.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c82ffc81851feaba75f0c127068dfa05dc7399b7.zip.