Yep, tracking pixels are among the oldest forms of internet surveillance, predating the far more aggressive and intrusive JavaScript companies use today. They'

Yep, tracking pixels are among the oldest forms of internet surveillance, predating the far more aggressive and intrusive JavaScript companies use today. They're one of the reasons why most mail clients don't load images by default. They only give information on page loads, not obsessive behavior tracking, but they're harder to block. They're why I block doubleclick.net, google-analytics.com, etc. in my hosts file rather than just blocking their JavaScript.