watchOS 5.1 (build 16R5568d) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-10-02T17:15:01Z. The update package is 590.94 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: 538335a0dade8ada90017c9d943d1aa1f3181c0c.zip.