title: tracking pixel asynchornous or synchronous
body: <p>I want to start using Google Tag Manager for all tags on websites, but I just read that it doesn't support synchronous tags.</p>
  
  <p>I'm not entirely sure if tracking pixel, image tags that have an external js as source, are in that category or not. I'm not sure if tracking pixels are blocking or not.</p>
  
  <p>Can someone please clarify why tracking pixels are or aren't synchronous?</p>