watchOS 6.3.1 (build 17U224) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2026-02-02T18:44:41Z. The update package is 542.55 MB. This is a delta (partial) update that requires 6.1.3 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 901c63061cfbdb8727d1dc479c21a8296ab12b81.zip.