Ads.txt for publishers

Programmatic buyers on the open exchange who think they’re purchasing inventory from ‘The New York Times’ often end up buying from imposter sites instead. At times, the amount of misrepresented inventory in the marketplace can dwarf the legitimate inventory sold by brand-name publishers.

IAB Tech Lab recently rolled out a new method for combating this ad fraud, specifically of the domain-spoofing variety. It’s called Ads.txt, which stands for Authorized Digital Sellers.


It is being seen as the opportunity to clean up the adtech ecosystem. As buyers, it is essential to understand who is authorized to sell authentic, premium inventory to ensure advertisers have access to the highest quality inventory. The ads.txt standard will act as a catalyst for eradicating publishers who falsify traffic sources. DSPs, SSPs and publishers and everyone in Ad Tech might need to move forward with ads.txt so we can get “bad guys” out of equation.


They are the ones selling counterfeit and misrepresented inventory on the exchange through their fake sites.

Unauthorized reselling is a major scourge in programmatic advertising, and unless buyers contacted publishers directly, they’ve had no way to know which SSPs are authorized to sell a particular publisher’s inventory.Creating a depository of authorized sellers should help buyers determine which programmatic firms have legitimate access to the inventory they seek.


Ads.txt is really straightforward. It’s a text file the publisher’s webmaster posts to the publisher domain. In that file is a list of authorized sellers (exchanges or SSPs) the publisher deals with. Buyers can then crawl the web for those lists, and create filters to assure they transact with those exchanges who are authorized to sell the publisher’s inventory.

Through the ads.txt initiative, the IAB Tech Lab is encouraging publishers to publicly declare select companies who are authorized to sell their digital inventory. With a goal of improving transparency in the programmatic supply chain, the ads.txt initiative enables buyers to easily identify authorized digital sellers and confidently buy authentic publisher inventory. This program will help eliminate any financial incentive from selling counterfeit and misrepresented media.


This is how a sample Ads.txt file of a premium publisher might look like.

Sample Ads.txt file for a premium publisher
  • Owned & Operated/ Direct: Your publisher page will be in a position to directly call these exchanges.
  • Authorized Reseller / Indirect: If you do not own and operate a site, but are authorized to sell you should ask the owner of the site to add this line to their ads.txt file:

The ads.txt implementation will ensure that those actors who don’t add value to the advertising chain, will disappear. Middlemen will take less of the margin, and both publishers and advertisers will see an increase in the value of their investment and content.


If a publisher does not implement ads.txt, it is assumed that anyone is authorized to sell their inventory. As ads.txt is adopted across the industry, this could be problematic for sellers as buyers could decide to use ads.txt to dictate their buying behavior and only buy from authorized sellers. Failure to incorporate this file and add all authorized sellers to it could lead to a decrease in ad revenue.


Not exactly.Like every initiative, this has its drawbacks too.

  • Ads.txt doesn’t cover all types of inventory reselling and misrepresentation for it doesn’t specify if a vendor is authorized to seller banner ads or video ads,leaving open a loophole for in-banner video arbitrageurs that represent display inventory as video inventory.“Display-to-video arbitrage is not necessarily solved by this, but it starts the conversation. Adding markers to include inventory type could become part of further iterations of ads.txt,,” Alanna Gombert (IAB) said.
  • The success of ads.txt depends on network effects because it will only be a reliable quick check for buyers should publishers and exchanges adopt it en masse. The program is in its initial stages and its integrations into exchanges are still being ironed out, so it’s too early to tell how popular the tool will become within the ad industry.
  • Publisher Yield can take a hit: Consider this instance:The advertising calls on this publisher’s page include calls to different platforms, such as DFP, which calls AppNexus. This is seen as legitimate because AppNexus is declared in the ads.txt file (as shown above). However, a typical ad call rarely stops there. AppNexus in turn calls AdForm (as seen below). AdForm isn’t declared within ads.txt as having a relationship with this publisher.

AppNexus is using AdForm as a demand partner, but AdForm could potentially call another DSP to purchase the inventory. If that DSP or even one of its direct advertisers crawls the ads.txt file and determines that AdForm doesn’t have a publically listed relationship with this publisher, they may demand a clawback or take other adverse actions against the platform, even if AdForm legitimately sold the inventory.

Some might argue that this is how the specification is intended to work by putting pressure on unlisted platforms and eventually eliminating them. But these platforms might also be providing better data, higher conversions or other data layers that contribute to the supply chain’s overall value by providing a high yield for publishers and higher conversions for advertisers.


I guess the right question is, “Are there any disadvantages for being transparent in the marketplace?”. For those publishers who aren’t transparent, yes there are a lot of disadvantages and revenue loss.

Even though it’s true that DSPs haven’t implemented ads.txt at a full scale yet, once they get all the industry push, especially from publishers, they’ll begin to do so. But there’s no a disadvantage for a publisher to have it implemented right away.

Ads.txt isn’t the solution to the ad fraud problem. Some in the industry are criticizing it because it solves one problem and not all quality issues the ecosystem has today. But we need to start somewhere to solve this problem, nobody learned to run without walking first.


Yes: take action now! Once we enter in the Q4 craziness, there is a sense of urgency that arises. It’s best to get going now and make sure ads.txt is properly integrated before it’s too late. ads.txt is very easy for publishers to implement, but it’s a bit harder for a DSP. It will be up to Publishers and SSPs to put some pressure on DSPs and advocate for this implementation in their technologies.

Work closely with your SSP(s) and resellers: it’s important for them to know when a Publisher implements ads.txt. More important, publishers need to make sure their partners stand by them during the process to ensure that the inventory is being sold only by the selected resellers.

Make sure buyers recognize publishers’ inventory and commitment: Publishers will lose out in the end if buyers don’t identify the inventory as a good content to include their ads. If that happens to any publisher, they should reach out to the reseller(s) and buyers to solve the problem as soon as possible.

As Manny Puentes of Rebel AI puts it, “ A certified letter might make its way through a number of post offices as it travels from Point A to Point B, but neither the sender nor recipient care how the letter arrives as long as it arrives in the right place. The same should be true in programmatic advertising.

But in ads.txt, the burden is put on the recipient to list all the possible post offices en route so the sender can feel more confident it ended up in the right place. While this might increase the feeling of transparency, it doesn’t solve the core objective.”

How it pans out, only time will tell.