watchOS 6.3 (build 17U216) is an official Apple over-the-air update for the Apple Watch Series 5 (40mm, LTE), released on 2021-01-26T18:27:24Z. The update package is 581.03 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: 43bb6a34ac18e57789e130891117650652ffe519.zip.