watchOS 5.1 (build 16R5589c) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2018-10-22T17:19:02Z. The update package is 389.89 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: c833426508259c3e1fb7bc9c465751697fa1a9b7.zip.