How does browser fingerprinting work?

When you visit a website, JavaScript on the page queries your browser for detailed information:

• Canvas fingerprint: your graphics card renders an invisible image; tiny differences in how hardware renders it create a unique ID
• Audio fingerprint: your audio system is queried similarly
• Installed fonts: tested by checking which characters render at which sizes
• Screen size, colour depth, pixel ratio: read directly
• Time zone, language, do-not-track setting: collected automatically
• WebRTC: can reveal your real local IP even behind a VPN

All values are combined into a single identifier. No single value is unique, but the combination typically is. This persists across sessions, private browsing, and different browsers on the same device.