watchOS 5.1 (build 16R5568d) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2018-10-02T17:14:27Z. The update package is 465.23 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: 6b166e4f60335024be5350895162504fab7b8ba3.zip.