watchOS 4.1 (build 15R5823c) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2017-09-27T16:59:28Z. The update package is 558.57 MB. This is a delta (partial) update that requires 3.2.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 35160973d51c0b24cbc95861ceda1ebfacabd796.zip.