watchOS 6.3 (build 17U208) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2020-12-14T18:08:55Z. The update package is 57.99 MB. This is a delta (partial) update that requires 6.2.9 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: b4765aa6399ca5c5594f73dade5f8050967d79a5.zip.