watchOS 5.1 (build 16R6591) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2018-10-30T17:21:16Z. The update package is 392.69 MB. This is a delta (partial) update that requires 5.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: ec5da1ad55cdd7d75fff928d394aeadaa144d633.zip.