watchOS 6.3.1 (build 17U224) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2026-02-02T18:44:23Z. The update package is 604.01 MB. This is a delta (partial) update that requires 6.1.2 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 6af7c4bdd944dfdc2018b39e4c52786f5a78b5f7.zip.