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VAST CORS Header Detector
Scan your VAST Video to check the CORS header.
Check 37+ ad quality tests for ad performance — validate against IAB VAST ad guidelines
CORS Header
The cross-origin resource sharing (CORS) header tells the browser if the document can be loaded from a different domain than on which it is hosted.
Why do we test it?
Without a proper CORS header, the browser won't be able to load the XML document. In that case, the video ads won't load and is considered a big configuration mistake.