watchOS 5.1 (build 16R5559d) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2018-09-18T17:22:34Z. The update package is 506.56 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: 7704338ac62b8a7ab34af67bb03c00c4c2b2c0e3.zip.