HTML5 may as well stand for Hey, Track Me Longtime 5. Ads can use it to fingerprint netizens

"In a presentation at Usenix's Enigma 2018 conference in California this week, Arvind Narayanan, an assistant professor of computer science at Princeton, showed how some of the advanced features of HTML5 – such as audio playback – can be used to identify individual browser types and follow them around online to get an idea of what they're into."