watchOS 5.1 (build 16R5584a) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2018-10-15T17:10:01Z. The update package is 431.88 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: c999517e41bb6720ff1e3204bdb16ab6328280ff.zip.