watchOS 6.3.1 (build 17U224) is an official Apple over-the-air update for the Apple Watch Series 5 (44mm, LTE), released on 2026-02-02T18:44:53Z. The update package is 557.1 MB. This is a delta (partial) update that requires 6.1 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: cd7a28788f413d4f546e19ac6274889b64f9ac1d.zip.