watchOS 5.1 (build 16R6591) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2018-10-30T17:21:17Z. The update package is 67.02 MB. This is a delta (partial) update that requires 5.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: a60ee17a4ec475d930ab3ad242ecac7f9fe6bf91.zip.