watchOS 6.1 (build 17S5054e) is an official Apple over-the-air update for the Apple Watch Series 4 (44mm, LTE), released on 2019-09-23T17:04:57Z. The update package is 711.41 MB. This is a delta (partial) update that requires 5.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 5524d08ccd7dd48e3d3a40f36b0dc7807059603d.zip.