A shopping site was playing a sound you can't hear, to work out which PC you are

A developer called Matt Callaghan noticed his Bluetooth headphones misbehaving. They'd stopped switching cleanly between his devices. He went looking for the cause and found it sitting in an open browser tab: AliExpress was playing him a sound he couldn't hear.

Not recording anything - playing. The site's scripts assembled a small audio pipeline inside the browser: an oscillator to generate a waveform, an analyser to measure what came back out, and the volume set to zero so nobody notices. The measurement is the point. Your browser, your version of Windows, your processor, your sound hardware and its drivers all handle that tone with tiny variations, and the pattern those variations make is close to unique to your machine. The same scripts also collected canvas rendering, WebGL data, your display settings and WebRTC behaviour. Put together, that lets a site recognise your PC on your next visit without setting a single cookie, and without anything you'd see in a privacy setting. Muting the tab doesn't help, because the sound never needed to be audible in the first place.

Brave, whose researchers went public on 22 August, blocks these particular scripts and has defended against audio fingerprinting for more than six years by handing sites randomised values instead of real ones. Firefox since version 118 sorts users into three broad groups by hardware type, which The Register reports makes the technique useless against 99.24% of them. Safari has its own tracking and fingerprinting protection. Chrome, which is what most people reading this are using, has the least of it. Alibaba hasn't commented.

Worth being straight about this one: there's nothing on your PC to find or remove, so no scan will help. The browser problem Tendvane does handle is the other kind - its "browser hijacked" repair wizard sorts out the extensions and changed search settings you genuinely never agreed to.