watchOS 5.1 (build 16R591) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-10-30T17:21:34Z. The update package is 763.78 MB. This is a delta (partial) update that requires 4.2.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: b065f4121b91dc23f48c8f274a19a12b0123de4c.zip.