watchOS 5.1 (build 16R5568d) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2018-10-02T17:14:48Z. The update package is 433.14 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: 04ea93eccb4e8137cd9bb510f189cdeefed3fa7e.zip.