watchOS 6.3.1 (build 17U224) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2026-02-02T18:44:21Z. The update package is 354.96 MB. This is a delta (partial) update that requires 6.2.1 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: a6234c84a23aeda059f1d538f88d0a0b66f706ec.zip.