watchOS 6.3 (build 17U208) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2020-12-14T18:08:52Z. The update package is 147.34 MB. This is a delta (partial) update that requires 6.2.5 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: fb52337c72e2eda33c0805b851f52d602fec4ebc.zip.