Ads.txt allows publishers to broadcast a list of authorized sellers of their ad inventory

The idea behind Ads.txt, which stands for Authorized Digital Sellers, is simple: by providing publishers with a means to tell the world who is authorized to sell their ad inventory, the digital ad ecosystem will get a much-needed boost of transparency that can help weed out scammers engaged in ad fraud.

The Ads.txt format is equally simple: an ads.txt file is hosted on publishers’ websites and contains a comma-delimited list of four fields (three required and one optional) and one record per line.

For example, a publisher,, to show that it has authorized a reseller,, to sell its inventory would include the following on a single line in its ads.txt file:, 12345, RESELLER

The IAB has built a crawler that the media buying ecosystem can use

The IAB is providing an open-source reference implementation for an Ads.txt crawler. This can be used by media buyers to create their own crawlers to pull Ads.txt data and incorporate it into their bidding systems.

Lots of companies have voiced support for it

Ad firms including Google, AppNexus, Rocket Fuel and The Trade Desk, as well as publishers like Business Insider, have voiced their support for Ads.txt.

According to Scott Spencer, Google’s Director of Sustainable Ads, “It’s great to see the industry moving quickly to address the issue of counterfeit inventory with Ads.txt. Google fully supports ads.txt, and with a finalized spec, we’ll begin integrating Ads.txt functionality into all our ads systems to make sure advertisers’ spend reaches the intended publishers.”

Ads.txt’s success will require mass adoption

While the initial support for Ads.txt looks promising, for it to become a truly powerful weapon in the fight against ad fraud, large percentages of both publishers and media buyers will need to follow through in adopting it. For example, if enough publishers don’t adopt Ads.txt, or a meaningful percentage of media buyers fail to take advantage of Ads.txt in their bidding, the specification will be for naught.

On the media buying side, a June article published by AdExchanger reported that “no buyers that AdExchanger spoke to had immediate plans to implement campaigns using ads.txt.”

According to Melissa Bonnick, VP of programmatic strategy at Havas Group’s programmatic trading desk Affiperf, “We will be paying attention to who starts to implement ads.txt.” Translation: we’re not going to incorporate Ads.txt into our bidding until there’s a good enough reason to do so.

There are reasons some publishers might not adopt Ads.txt

While Ads.txt is relatively easy for publishers to adopt, there are a number of reasons that some publishers might not opt to do so.

One of the biggest: even though transparency is a good word in the digital advertising ecosystem today, when push comes to shove, some publishers are likely to be uncomfortable letting the world know who is selling their inventory.