watchOS 5.1 (build 16R5584a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-10-15T17:10:07Z. The update package is 424.17 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: bd639e713c9abcffe0f5b0a73db88f55291258a4.zip.