watchOS 9.0 (build 13S344) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2015-09-21T17:58:03Z. The update package is 515.79 MB. This is a delta (partial) update that requires 8.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 11c916617ab55d9df785b61248d8fb6a64888bf4.zip.