watchOS 5.1 (build 16R5584a) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2018-10-15T17:09:18Z. The update package is 738.66 MB. This is a delta (partial) update that requires 4.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: bc6b7fd6b2e2fd64d67e6444a3d6869438b8a150.zip.