System fonts
GET /api/fingerprint/fontsFont fingerprinting identifies installed system fonts by measuring text rendering dimensions. The technique works by creating invisible DOM elements with specific fonts applied, measuring their rendered width and height, and comparing against known dimensions for different fonts. Since text renders differently depending on which fonts are available, measuring the same text string with different font-family declarations reveals which fonts are installed. Operating systems ship with different default font sets (Arial, Helvetica, Times New Roman, etc.), and users often install additional fonts for professional work, games, or design applications. The combination of installed fonts creates a highly distinctive fingerprint. For example, Adobe Creative Cloud users typically have hundreds of Adobe-branded fonts, programmers install coding fonts like Fira Code or JetBrains Mono, and gamers may have game-specific fonts. Font fingerprinting can distinguish between Windows, macOS, and Linux systems based on default fonts, identify specific OS versions (Windows 11 vs. Windows 10), detect language packs, and even infer user professions based on specialized fonts. Privacy browsers attempt to restrict font enumeration by limiting font access or returning standard font sets, but this makes users more identifiable by their unusual font configuration.
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