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 261.27 MB. This is a delta (partial) update that requires 6.2.6 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 4a5b62c72d9c6d3fb1d2ec1a9799caaaaeb548e4.zip.