AliExpress discovered using audio fingerprinting to track users

AliExpress has been discovered using a technique known as audio fingerprinting to track users without their consent or the use of traditional cookies. The method was identified by developer Matt Callaghan after his Bluetooth headphones unexpectedly disconnected from his smartphone to connect to his computer while he was browsing the site.

Investigation revealed that the platform used scripts to trigger the Web Audio API, generating a silent sawtooth wave. By measuring how a user's specific device processed this sound, the site could create a unique digital fingerprint to identify returning users for targeted marketing. Because the volume was set to zero, the process remained undetectable to the user, even if they muted the browser or the system.

While security experts note that browser fingerprinting is a widespread practice, the use of audio-based methods is a specific approach to bypassing privacy protections. Browsers such as Brave, Mozilla Firefox, and Tor are noted for having mechanisms to defend against such tracking methods.