watchOS 5.1 (build 16R5584a) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2018-10-15T17:09:36Z. The update package is 118.47 MB. This is a delta (partial) update that requires 5.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: e1e7f8da440eaee6cddec7bf18dd18ab1473cd32.zip.