Browser Fingerprinting: How Websites Track You Without Cookies

Even without cookies, websites can uniquely identify your browser through fingerprinting — collecting device characteristics that create a unique identifier.

Data Points Collected

Canvas rendering (GPU-specific patterns), WebGL renderer info, installed fonts list, screen resolution and color depth, timezone and language, audio processing fingerprint, available plugins, HTTP headers, CSS media queries, JavaScript engine quirks. Combined, these create a fingerprint unique to 1 in 286,777 browsers according to EFF research.

How Tor Browser Defends

Tor Browser uses 'uniformity' as its defense: all Tor Browser users appear identical. Canvas fingerprinting returns blank or randomized data. Standard window size prevents resolution fingerprinting. System fonts are restricted. WebGL is disabled at higher security levels. All Tor Browser users share the same user agent string.

What Breaks This Protection

Resizing the browser window. Installing extensions. Allowing JavaScript on sites that probe for fingerprint data. Using Tor Browser on unusual operating systems. Changing default settings. Each deviation from the default makes you stand out from the crowd of Tor users.