🔤 Font Fingerprint

Font fingerprinting identifies your device by detecting which fonts are installed on your system. Different operating systems, software installations, and user preferences create unique font combinations.

🔬 How Font Detection Works

Websites can't directly list your fonts, but they can detect them through rendering:

1. Create a hidden text element
2. Set the font to a test font with fallback
3. Measure the text width
4. If width differs from fallback, font is installed

// Font detection technique
function isFontInstalled(fontName) {
    const testString = 'mmmmmmmmmmlli';
    const testSize = '72px';
    
    const canvas = document.createElement('canvas');
    const ctx = canvas.getContext('2d');
    
    // Measure with fallback font
    ctx.font = testSize + ' monospace';
    const fallbackWidth = ctx.measureText(testString).width;
    
    // Measure with test font
    ctx.font = testSize + ' "' + fontName + '", monospace';
    const testWidth = ctx.measureText(testString).width;
    
    return fallbackWidth !== testWidth;
}

📊 What Fonts Reveal

🛡️ Font Spoofing Techniques

1. Font List Filtering

Report only a subset of common fonts that match the spoofed OS.

2. Font Emulation

Make the browser report fonts that aren't actually installed.

3. Rendering Modification

Modify how fonts render to create consistent fingerprints.

❓ FAQ

🔗 Related Terms