watchOS 5.1 (build 16R5584a) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm), released on 2018-10-15T17:10:24Z. The update package is 160.21 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: 7cc97bb2a59e0a5742c6ee430d243ca1d4add9a0.zip.