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fingerprintingaudiofonts

Audio and font fingerprinting

Two quieter tracking signals — the Web Audio API and installed fonts — and how to keep both consistent with a profile's platform.

VTVeilBrowser Team2 min
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Audio and font fingerprinting

TL;DR

Audio fingerprinting hashes tiny differences in how your device processes sound. Font fingerprinting detects exactly which fonts you have installed. Both leak your platform. A consistent profile ships a platform-matched font set and stable audio output.

Canvas and WebGL get the attention, but two quieter signals — audio and fonts — are just as useful to trackers, and just as easy to get wrong when spoofing.

An audio waveform and a grid of font glyph specimens

Audio fingerprinting

The Web Audio API can generate and process a signal entirely offline with OfflineAudioContext. The exact floating-point output depends on the device's audio stack, so hashing it yields a stable identifier.

audio-probe.js
const ctx = new OfflineAudioContext(1, 44100, 44100);
const osc = ctx.createOscillator();
osc.type = "triangle";
osc.frequency.value = 10000;
osc.connect(ctx.destination);
osc.start(0);
const buffer = await ctx.startRendering();
// hash the samples in `buffer`

As with canvas, the fix is a stable value per profile that matches the platform — not per-request noise.

Font fingerprinting

Sites detect installed fonts by measuring the width and height of text rendered in each candidate font, comparing against a fallback. The set of fonts that render differently reveals which are installed — and font sets are strongly tied to the operating system.

The danger for spoofing: if a profile claims Windows but exposes the macOS system fonts (or a Linux server's font set), the mismatch is obvious. This is a common way headless automation on Linux gets flagged.

Keeping both consistent

A believable profile:

  • Ships a platform-matched font pack so a Windows profile exposes Windows fonts, even when the browser runs on Linux.
  • Produces a stable audio hash per profile, consistent with the platform.
  • Keeps these aligned with the canvas, GPU and user-agent.

VeilBrowser bundles platform font packs and controls audio at the browser level so host fonts never leak during cross-OS operation. See the platform docs.

FAQ

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Run cross-platform profiles without leaking host fonts or audio traits. Start free or read about profiles.

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