watchOS 5.1 (build 16R5568d) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2018-10-02T17:14:23Z. The update package is 733.49 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: 6b3a24d80d580acb43132c8628364c3ec6a17a8c.zip.