watchOS 6.3 (build 17U216) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2021-01-26T18:26:20Z. The update package is 504.58 MB. This is a delta (partial) update that requires 6.1.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 31c2d1c65b969b12fef368bbeb3194fcebade3de.zip.