watchOS 6.3 (build 17U216) is an official Apple over-the-air update for the Apple Watch Series 4 (40mm), released on 2021-01-26T18:26:48Z. The update package is 557.01 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: 5e09e103e48cde05721ac3aee21551f3ad4c1f10.zip.