watchOS 6.1 (build 17S5076a) is an official Apple over-the-air update for the Apple Watch Series 4 (40mm, LTE), released on 2019-10-16T17:13:51Z. The update package is 365.78 MB. This is a delta (partial) update that requires 6.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c8b9b664e2c72dbcb8043c00b850c6332d453c54.zip.