watchOS 6.3 (build 17U208) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2020-12-14T18:08:50Z. The update package is 174.52 MB. This is a delta (partial) update that requires 6.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 226fe0894d71dbc9d689cae3c6408cbe9e511982.zip.