watchOS 6.3 (build 17U216) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2021-01-26T18:26:58Z. The update package is 173.79 MB. This is a delta (partial) update that requires 6.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 2e48d08d20c77dd3a192c0e9fa592569464c5bf9.zip.