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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 and validate against IAB VAST ad guidelines

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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.