watchOS 6.3 (build 17U216) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2021-01-26T18:27:12Z. The update package is 445.29 MB. This is a delta (partial) update that requires 6.1.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 50cdbba6597772e2e62b1a1ce248c287126cef52.zip.