User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:69.0) Gecko/20100101 Firefox/69.0

Expected results:

When you have a CORS problem, only the console displays the error/warning.

It could be great to have something which notifies a CORS problem like :

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at xxx/api/bills/18. (Reason: CORS header 'Access-Control-Allow-Origin' does not match 'yyy')

directly into the network panel on the line of the request having some CORS troubles.

More information on slack: https://devtools-html.slack.com/archives/C3ZTF8URG/p1561561205014500

My first reflex when a XHR or Fetch request seems to have no effect in the page (or shows an error state in the page) is to look in the Network panel for stuff like 404s and 500s. Having CORS issues spelled out there would help, meeting me where I'm looking already.

Do we have similar feedback from other users already? How can we tell if it would be helpful to many and not just to a few?

On the UI side, maybe the way we alert about tracking protection in Netmonitor could be reused and expanded upon?

Yes, agree, this would be great feature.
Honza

Maybe a dupe of bug 1445637 and bug 1564011.

Agree, marked as dup.
Honza