“CAUTION: provisional headers are shown” in Chrome debugger

Question

I noticed a strange caution message when looking at downloaded resources using Google chrome inspector (F12):

Caution provisional headers a

Answer 1

A common reason this happens is if you are tracking an event and you don't prevent the default action. For example, if you have a click event, then you will want to include:

e.preventDefault();

or

return false;

If you don't, you will see the provisional headers warning as well as a "canceled" status in the Network tab of your web console.