watchOS 6.3.1 (build 17U224) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2026-02-02T18:44:21Z. The update package is 304.76 MB. This is a delta (partial) update that requires 6.2.5 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: e8b4b3cdb2c8e8ddf678e75a0fc04c1d25e75022.zip.