TextMetrics

Textmetrics fingerprinting takes advantage of the way different devices and browsers render text. Slight differences in text rendering—due to variations in graphics processing units (GPUs), font versions, OS implementations, and browser nuances—can produce unique profiles for devices.

This technique assesses various parameters:

• Specific fonts available on a device
• How a browser renders particular characters or fonts
• Pixel-level differences in text display

When combined, these metrics produce a fingerprint that can be surprisingly distinctive for individual users.

Implementing Textmetrics Fingerprinting in JavaScript#

Here’s a simplified version to give you a taste of how it works:

function getTextMetrics() {
    // Create an off-screen canvas element
    let canvas = document.createElement("canvas");
    canvas.width = 500;
    canvas.height = 200;
    let ctx = canvas.getContext("2d");

    // Render some text on the canvas
    ctx.font = "16px Arial";
    ctx.fillText("Sample Fingerprinting Text", 50, 50);

    // Get pixel data
    let data = ctx.getImageData(0, 0, canvas.width, canvas.height).data;

    // Hash the data for a more concise fingerprint
    let hash = 0;
    for (let i = 0; i < data.length; i++) {
        hash = (hash << 5) - hash + data[i];
        hash = hash & hash;
    }

    return hash;
}

let fingerprint = getTextMetrics();
console.log("Your textmetrics fingerprint:", fingerprint);

This script creates an off-screen canvas, draws a sample text, then processes the pixel data to produce a unique fingerprint hash.