watchOS 6.3.1 (build 17U224) is an official Apple over-the-air update for the Apple Watch Series 5 (40mm, LTE), released on 2026-02-02T18:44:50Z. The update package is 542.68 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: d86d20ab66c430ed5b6289f90417c2c11287027b.zip.