watchOS 6.3 (build 17U216) is an official Apple over-the-air update for the Apple Watch Series 4 (40mm, LTE), released on 2021-01-26T18:27:03Z. The update package is 580.31 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: 774494ff13d924a920fd07bb9b2e561a307f6ef7.zip.