What is Ads.txt and Why is ads.txt important to buyers and sellers?

In this world, so many brands, publishers, industry, and agencies become part of the programmatic advertising’s transparency, so that for Increase transparency in the programmatic advertising ecosystem, Interactive Advertising Bureau has come up with a great strategy, i.e. ads.txt. The Interactive Advertising Bureau Tech Lab introduced ads.txt as a tool that can help ad buyers avoid illegitimate sellers who arbitrage inventory and spoof domains.

What is ads.txt?

Ads.txt means for Authorized Digital Sellers. It is an IAB-approved text file. It’s an informal way for publishers to plainly indicate to buyers who are authorised to sell their inventory. The purpose of the tool is to increase transparency in the programmatic advertising ecosystem. Ads.txt will help publishers to permit a public declaration of the companies approved to sell their digital inventory. It is Like robots.txt, ads.txt can only be posted to a domain by a publisher’s webmaster, making it valid and authentic. It is easy to update, making it flexible. The data essential to populate the file is readily available in the OpenRTB protocol.

How Does It Work?

Programmatic platforms will assimilate ads.txt files to check which publishers inventory they are authorised to sell. It will allow buyers to check the validity of the inventory they purchase. The publisher puts a text file in the web server on the root level of the domain (

It’s looking like CSV format, which could either be simply a file or dynamically generated, just named ads.txt. Publishers should add the “/ads.txt” file on their root domain and not on subdomains. The buyers can then crawl the web for publisher ads.txt files to create a list of authorised sellers for each participating publisher. Then programmatic buyers can create a screen to match their ads.txt list against the data provided in the OpenRTB bid request.

For Example:

Here is how the process would work?

  • Publisher ID linked to your account on an exchange or supply-side platform
  • Publisher IDs that are approved to sell their ad-space in a file called Ads.txt on their domain, g.
  • Demand-side platform crawls the domains they’ve previously served impressions on looking for this /ads.txt.
  • This publisher ID should be transmitted through the OpenRTB protocol as the publisher ID, along with the Publisher. Once a brand or advertiser has a list of publishers that use ads.txt, they can orientation this list against IDs in OpenRTB bid requests.

(< SSP Domain >, < Publisher ID >, < Account type >, < TAGID >)

  • If no ads.txt is present, it will consider open for any Exchange to sell
  • If the Seller Account IDs match, then the buyers know that the publisher is who they say they are.
  • If they don’t match or don’t exist, then it could mean that the domain is not coming from an authorised dealer or that the publisher hasn’t implemented ads.txt, and the buyers can choose not to bid on that inventory.
Why Do We Need?

If a publisher does not implement ads.txt, that means anyone is authorised to sell their inventory. It is crucial for each website to get the file and implement it correctly, for contributing publishers, know that unauthorised sells will lead to advertiser declining buying ads from your site.

Ads.txt prepared for the most common formats, i.e. Banner, Audio, Video, Native. Along with that, several publishers partner with different exchanges for different ad formats. That means publishers must reach out many platforms to gather their seller accounts’ IDs in a single place.

Why is ads.txt important to buyers and sellers?

It can help you block undesirable advertisers from running on your site and improve ad quality as well as user experience, regarding all kind of malicious bad quality ads. Furthermore, as sellers and buyers will be expecting Ads.txt on publishers’ websites, publishers with Ads.txt in place will be regarded as more trustworthy.


Ads.txt can help you prove direct relations with your supply sources and increase revenue, as well as improve traffic quality and transparency. Programmatic buyers purchase inventory only from pre-authorised sellers.  DSPs are then able to collect all the ads.txt files available.  They can check whether there is a corresponding entry in the ads.txt file for the publisher and adjust their bid accordingly.