Browser Fingerprinting as a Tracking Technology
Browser fingerprinting is a technique that uniquely identifies users based on the combination of settings and characteristics of their web browser and device. Because it does not require storing any data on the device — unlike cookies — it is sometimes called a "stateless tracking technology."
Screen resolution, installed fonts, browser version — each piece of information individually is shared by many users. However, when combined, they can identify individual browsers with remarkable accuracy. Research suggests that browser fingerprints achieve a uniqueness rate of 80–90% or higher.
What Information Is Collected?
Basic Browser Information
- User-Agent string (browser type, version, and OS information)
- Language settings and language priority order
- Time zone
- Do Not Track setting
- Cookie enabled/disabled status
Screen and Display Information
- Screen resolution and color depth
- Device pixel ratio (used to detect Retina displays, etc.)
- Available screen size (effective area excluding taskbars, etc.)
Hardware Information
- Number of logical CPU cores
- Device memory capacity
- GPU type (obtained via WebGL)
- Touchscreen availability and number of touch points
Advanced Fingerprinting Techniques
- Canvas fingerprinting: Generates a unique hash from pixel data rendered on an HTML5 Canvas element
- AudioContext fingerprinting: Uses the Web Audio API to detect subtle differences in audio processing
- WebGL fingerprinting: Identifies GPU-specific characteristics from 3D graphics rendering results
Entropy and Uniqueness
The discriminating power of a fingerprint is measured by "entropy," expressed in bits — the higher the value, the greater the identifying power.
For example, users with a screen resolution of "1920×1080" make up roughly 30% of all users, so this attribute alone has relatively low entropy. In contrast, GPU renderer strings are extremely diverse and carry high entropy.
The Kakunin-san fingerprint uniqueness score visually displays the entropy contribution of each attribute, giving you a numerical measure of how unique your browser is.
How Fingerprinting Is Used
Ad Tracking
Advertising networks use fingerprinting as an alternative to cookies for tracking user behavior across websites. Because fingerprint-based tracking persists even after cookies are deleted, it is a more tenacious form of surveillance.
Fraud Detection
Financial institutions and e-commerce sites use fingerprinting to detect unauthorized access and account takeovers. When access from an unusual fingerprint is detected, additional authentication may be required.
Bot Detection
Fingerprinting is also used to distinguish automated access (bots) from human visitors. Bots typically exhibit distinctive fingerprint patterns.
How to Protect Yourself from Fingerprinting
Complete protection is difficult, but the following measures can significantly reduce tracking risk.
Choose a Privacy-Focused Browser
The Tor Browser is designed so that all users share an identical fingerprint, making it the most effective countermeasure. The Brave browser also includes built-in fingerprint protection features.
Use Browser Extensions
- Canvas Blocker: Randomizes or blocks Canvas fingerprinting
- User-Agent Switcher: Spoofs the User-Agent string to a common value
- Privacy Badger: Automatically learns and blocks trackers
Review Your Browser Settings
- Disable WebGL (may affect rendering on some sites)
- Restrict JavaScript execution (many fingerprinting techniques depend on JS)
- Block third-party cookies
Combine with a VPN
A VPN can hide your IP address and time zone information, but it cannot prevent fingerprinting itself. Combining a VPN with fingerprint countermeasures provides more robust privacy protection.
Summary
Browser fingerprinting is a powerful tracking technology that serves as an alternative to cookies. Knowing how unique your browser is represents the first step toward protecting your privacy. Check your Kakunin-san fingerprint uniqueness score right now.