watchOS 6.3.1 (build 17U224) is an official Apple over-the-air update for the Apple Watch Series 4 (40mm), released on 2026-02-02T18:44:33Z. The update package is 154.95 MB. This is a delta (partial) update that requires 6.3 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: a3ac96f5cb1aa3a9aa35d35fa1c985d8eea7e599.zip.