watchOS 5.1 (build 16R5589c) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2018-10-22T17:19:08Z. The update package is 733.17 MB. This is a delta (partial) update that requires 4.3.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 8ec915af7639b5ac877f85b6164d8fbb150c7459.zip.