Pressure sensitivity is now exposed by the browser's Pointer Events API for all supported tablets (not just Wacom). Pointer events such as onpointermove will contain a "pressure" field that ranges between 0.0 and 1.0.
Pointer Events are supported by Chrome, Firefox, Internet Explorer (10+), Microsoft Edge and Safari (13+) on macOS and Windows 8+ (Windows 7 doesn't provide pressure information). See: