Developers can now get their hands on the third beta version of watchOS 3. The configuration file is available from the Apple Developer Download site, while the update itself can be downloaded and installed from an iPhone running the latest beta of iOS 10.
When it arrives for the Apple Watch this fall, watchOS 3 will focus on major enhancements to speed, particularly for launching apps. People will now be able to keep a number of apps in the new watch dock for easy access and quick launching. Apps will also be able to fetch background updates.
Apple occasionally offers updates to iOS 10, watchOS 3, tvOS 10, and macOS Sierra as closed developer previews or public betas for iPhone, iPad, and Mac. (Sadly, no public betas for the Apple Watch or tvOS.) While the betas contain new features, they also contain pre-release bugs that can prevent the normal use of your iPhone, iPad, Apple Watch, Apple TV, or Mac, and are not intended for everyday use on a primary device. That's why we strongly recommend staying away from developer previews unless you need them for software development, and using the public betas with caution. If you depend on your devices, wait for the final release.