watchOS 3.1.3 (build 14S959) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2017-01-09T17:56:45Z. The update package is 18.01 MB. This is a delta (partial) update that requires 3.1.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 82388a220ef7e60c0aaff2a4f182807b0b9d652a.zip.