AliExpress slipped inaudible audio into web pages to tag browsers without user consent. The move resurrects a tracking method many thought dead, and it forces engineers to rethink the assumptions behind web privacy.

Ars Technica reported that the e‑commerce giant injected sound bursts that humans cannot hear but that browsers can capture and translate into a unique fingerprint. The technique is old, the report says, and it is sti…

The method relies on the speaker‑microphone loop that every modern device possesses. A web page plays a tone at a frequency beyond the audible range, typically above 18 kHz. The browser records the echo that bounces o…

Because the signal never reaches the user’s ears, the process is invisible. The hash can be sent back to a server and linked to other identifiers such as cookies or IP addresses. The result is a persistent identifier …