Did you know that browsers can produce audio files you can’t hear, and those audio files can be used to identify web visitors? Apple knows, and the company decided to fight the identification possibility in Safari 17, but their measures don’t fully work.
Identifying with audio
The technique is called audio fingerprinting, and you can learn how it works in our previous article. In a nutshell, audio fingerprinting uses the browser’s Audio API to render an audio signal with OfflineAudioContext interface, which then transforms into a single number by adding all audio signal samples together. The number is the fingerprint, also called “identifier”.
The audio identifier is stable, meaning it doesn’t change when you clear the cookies or go into incognito mode. This is the key feature of fingerprinting. However, the identifier is not very unique, and many users can have the same identifier.