2 Compatible Devices
watchOS 5 update is available for nearly all available Apple Watch models, with one notable exception.
At launch, watchOS 5 will be supported by the Apple Watch Series 1, Apple Watch Series 2 and Apple Watch Series 3. It’ll come preinstalled on Apple Watch Series 4.
But the new update is not supported by the original Apple Watch released in 2015 (often called the Apple Watch Series 0 or first-generation), however.
To download and use watchOS 5, you’ll also need an iPhone 5s or later running at least iOS 12.