Capabilities
What a device can actually do.
Every field is the result of a probe, never an inference from a version number: availability is a property of the WebView build on the device, and that updates independently of the operating system. A capability reported here as present never raises ErrorCode.UNSUPPORTED in use; one reported absent raises it immediately rather than timing out.
Properties
Scripts can be installed before any page script runs.
The protocol backend connected. False means the platform backend serves everything.
The renderer reports responsiveness, so a hung page is detectable before it crashes.
This session can produce a screenshot. Requires a viewport-sized session.
Requests issued by a service worker can be intercepted.
The typed, origin-scoped channel from page context to native code is available.