What is Canvas Fingerprinting?
A browser fingerprinting technique that exploits the HTML5 Canvas element to identify users based on how their GPU renders graphics.
Canvas fingerprinting generates a unique identifier by asking your browser to draw an invisible image and analyzing the result.
How It Works
- A script creates a hidden Canvas element
- Draws text and shapes using specific fonts and rendering
- Reads the pixel data back
- Different hardware, drivers, and OS produce slightly different outputs
- The hash of the output serves as a fingerprint
Why Outputs Differ
- GPU hardware differences affect rendering
- Font rasterization varies across operating systems
- Anti-aliasing algorithms differ
- Sub-pixel rendering settings vary
Detection and Blocking
- CanvasBlocker extension for Firefox
- Brave Browser adds randomness to Canvas output
- Tor Browser returns a blank/uniform Canvas result
- Privacy-focused browsers can notify you when Canvas fingerprinting is attempted
Related Terms
Browser Fingerprinting
A tracking technique that collects information about your browser, device, and settings to create a unique identifier. Unlike cookies, fingerprints are nearly impossible to delete and can track you across websites without your knowledge or consent.
WebRTC Leak
A browser vulnerability where WebRTC (used for video calls and peer-to-peer communication) reveals your real IP address even when using a VPN, because WebRTC can access your network interfaces directly.
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