During Q1 2018, The Guardian worked with Google and MightyHive to determine how much of the inventory on ad exchanges purporting to belong to The Guardian was indeed legit. They used ads.txt—a text file on publishers’ sites that lists the vendors that have permission to sell their inventory—to accomplish this. Many ad buying platforms give advertisers the ability to restrict their purchases to inventory that is validated by ads.txt. About eight in 10 publishers who sell inventory programmatically have adopted ads.txt, according to Adzerk.
The Guardian and its research partners found that when ads.txt filters were applied to their ad buys, there were no discrepancies between what they bought and what ended up coming back to The Guardian. But when ads.txt filters were not applied, 1% of display ad spend and 72% of video ad spend went to unauthorized programmatic platforms. Read the rest at eMarketer.