Font Fingerprinting

Font fingerprinting is a browser fingerprinting technique that identifies and tracks users based on the unique set of fonts installed on their devices. By querying which fonts are available and how they render, websites can create a distinctive profile that helps differentiate users even without cookies or IP tracking.

Also known as: Font enumeration, Font detection

Comparisons

• Font Fingerprinting vs. Canvas Fingerprinting: Font fingerprinting relies on installed fonts and their rendering, while canvas fingerprinting uses graphic rendering differences.
• Font Fingerprinting vs. User Agent: Font fingerprinting provides more detailed uniqueness beyond basic browser and OS info found in user agents.

Pros

• Enhanced User Identification: Provides an additional layer of user identification for analytics and fraud detection.
• Cookie-Independent Tracking: Works even when cookies or other tracking methods are disabled.

Cons

• Privacy Implications: Raises privacy concerns as it enables user tracking without clear consent, potentially bypassing user preferences or regulations.

• Partial Mitigation Available: Can be reduced or prevented by disabling or limiting font enumeration in certain browsers, though this may impact functionality.

Example

When a website checks which fonts your browser can access and notices you have a rare combination like “Comic Sans MS,” “Courier New,” and some custom fonts installed, it can use this information to distinguish your device from others, helping track your visits across sessions.