watchOS 5.1.3 (build 16S535) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2019-01-22T18:11:30Z. The update package is 980.56 MB. This is a delta (partial) update that requires 3.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d76efea78a0e3f679e9aacdbe006327598ac0347.zip.