watchOS 5.1 (build 16R5568d) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2018-10-02T17:15:12Z. The update package is 166.6 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: c831670c2cf7cf487f7b449a2a07d7dccffb8d8a.zip.