BrowserLeaks

The most thorough browser leak testing suite out there. Tests everything a website can potentially extract from you: Canvas, WebGL, WebRTC, fonts, screen resolution, audio fingerprint, CPU cores, memory, Battery API and dozens more. Unlike Whoer or PixelScan which give you a score, BrowserLeaks shows the raw data itself. Useful when you need to understand exactly what's leaking and why, not just "something is wrong".