Same ad script.
Two routes.

Each vendor script loads once from its normal hostname and once through a first-party EasyProxy hostname. Turn your ad blocker on, rerun the test, and compare the result cell-for-cell.

Every cell runs in a separate srcdoc iframe so vendor globals and singleton SDKs cannot collide. A check means the script response reached the browser and fired its load event; it does not simulate an ad auction, impression, or conversion. A cross means the browser, extension, DNS filter, or network prevented delivery.