This is a performance measurement demo.

It should make a request for p.js, schedule and run some jobs, then beacon the serialized metrics

If you can't see that in the network activity, probably uBlock or similar is blocking

Evidently in IE a customer says when the devtools are open, a breakpoint gets hit. I don't know more right now, but wonder if that was an exception being thrown

Could you try this in IE11 and report back? :))))