watchOS 3.1.3 (build 14S959) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2017-01-09T17:56:29Z. The update package is 126.72 MB. This is a delta (partial) update that requires 3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: f2d57b9201ab3c61169f562f8c5e953a36150574.zip.