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Not monitoring your Ads.txt files? Reset your expectations

Ad tech is a dynamic space to work in. From bidding algorithms to virtual reality and blockchain to machine learning, there is always cutting-edge technology being applied to how we serve ads. You might not think of it as rocket science, but I happen to know of at least two people in ad tech that are actual rocket scientists.

These advanced concepts are what makes ads.txt so fascinating. Ads.txt (the “inventor” Neil Reichter pronounces it ads dot tee x tee, but dot-text is fine) is a simple text file. A publisher uploads their ads.txt file to their website (go to to see it). The simple act of publishing this file is a key deterrent to fraudsters looking to rip off the industry via a trick called “domain spoofing”.

Domain spoofing is relatively easy to pull off. In the world of programmatic buying, ad impressions on websites are bid upon based on what the buyer knows about the user viewing the impression, the site and context in which the impression is being served. If I’m a premium brand, my preference would be to show my brand’s ad on a site like the New York Times instead of Bob’s News. In fact, as a buyer I’m certain to pay more for the higher-value opportunity. Bob, who runs a fraudulent website, knows this. To make more money, Bob will tell the ad exchange that the impressions running on Bob’s News are running on the New York Times. If the exchange doesn’t pay attention nor does the buyer, Bob can make a lot of money by simply spoofing the New York Times.

Ads.txt makes domain spoofing as described nearly impossible (we in the ad tech world know better than to make absolute statements about what can and can’t be done). As a buyer or exchange, I can check an ad impression against a websites ads.txt file. If something doesn’t match up, I shouldn’t buy it. If I do buy it, the ads.txt makes sure the correct site makes the money. Bob can say he’s the New York Times and if he does, the New York Times would get paid and Bob would make nothing. Bob therefore no longer has a financial interest in domain spoofing.

Ads.txt is so simple that nearly every publisher in the top 5,000 by Quantcast ranking has an ads.txt in place. In many respects, it’s probably the most rapidly adopted standard ever in ad tech. Groups including the IAB, IAB UK and TAG (Trustworthy Accountability Group) now require it. So what’s the problem?

The problem is many ads.txt files are inaccurate. They either include publisher partners that are not actually partners or some partners are not listed when they should be. Some publishers simply make typing errors and have the wrong information in the ads.txt file. The wrong ads.txt information is the same as having no ads.txt information.

Industry Index was asked to analyze ads.txt information in their database for the top 5,000 publishers (again, by Quantcast ranking). They reported that while 4,948 publishers have Google Ad Manager tags on their pages (almost 99%), 708 of those same sites did not have Google properly listed in their ads.txt files (14%). Similarly, 3,786 of these same publishers have OpenX listed, but 1,065 (28%) did not have OpenX actually active on their site.

The reason for these disconnects is simple: some publishers don’t see ads.txt as important, or important enough. The other reason? Things happen quickly, and relationships between partners and their partners’ partners are so complex, publishers can’t keep track of it all. They need tools and outside vendors who are purpose-built to continually help track and identify such changes.

Fortunately, partners exist who help facilitate ads.txt management. Typically, such tools help publishers understand who might be collecting information on users without their permission, or which partners might prevent them from being GDPR-compliant by letting third-parties collect data. Part of Industry Index’s solution, for example, is to scan publishers’ sites and track what is actually happening with technology partners vs. what is stated in an ads.txt file. They see this as an important first line of defence.

“We are truly surprised at the number of mismatches between active technologies and what is listed in ads.txt files,” said Jonathon Shaevitz, President of Industry Index. “99% of the top 5,000 publishers had at least one error, and a little over 50% have more than five conflicts between what is in their ads.txt file and their technology installations. We know that almost 80% of these publishers have quality demand sources active on their site, but not in their ads.txt file. That’s a lot of missed revenue.”

Ads.txt has made domain spoofing much harder for fraudsters to do. Simply putting a text file on your website, however, isn’t enough. Constant monitoring by the publisher and perhaps with the help of a partner is the only way to make sure ads.txt is doing its job.

Rob Beeler  @rbeeler

As Chairman of AdMonsters and Founder of Beeler.Tech, Rob has 20+ years in digital media and ad tech. He provides guidance to the industry through training, consulting, events and research.

Industry figures and insights provided courtesy of Industry Index, who tracks the MarTech & AdTech ecosystem with monitoring and insights tools for data leakage, tech usage, and publisher ad ops.

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