watchOS 6.3 (build 17U216) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2021-01-26T18:26:57Z. The update package is 436.06 MB. This is a delta (partial) update that requires 6.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c2ae41eaecc99bd493523b12f592754b66fd9edf.zip.