watchOS 6.3.1 (build 17U224) is an official Apple over-the-air update for the Apple Watch Series 4 (40mm, LTE), released on 2026-02-02T18:44:40Z. The update package is 188 MB. This is a delta (partial) update that requires 6.2.8 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: fdc156b85a4e31317725a471959e984f7be3fbf3.zip.