Video Monetization

Ads.txt: The brand safety initiative that is now a requirement for online publishers

By Milen Debensason | Oct 2, 2017


You’ve probably heard about the new initiative led by IAB called ads.txt. This is an important step toward fighting fraudulent activity by creating more transparency in the advertising ecosystem – and Google agrees. According to their newsletter:

“At the end of October, domains where the seller’s Publisher ID is not present in the ads.txt file may no longer be monetized through Ad Exchange. Google will also stop buying ads on such sites. We recommend that you work with your Network Partners to include your Publisher ID in their ads.txt files in order to prevent impact to your earnings.”

While Google may be the first to implement this rule, it’s extremely likely that similar statements will be coming from other SSPs in the near future. So it’s best for publishers to consider adding ads.txt files as not just an initiative, but a requirement, as soon as possible – for the betterment of all parties involved. Here’s everything that publishers should know about ads.txt:

What is Ads.txt?

To really understand what ads.txt is all about, let’s compare a publisher’s website to a physical store that sells watches. Let’s say this store has been given permission by an expensive luxury watch brand “LuxWatch” to be an authorized seller of their watches, and this store’s owner has placed their permission document at the storefront so each buyer can see it. The watch store next door was also authorized to sell LuxWatches, but their store owner forgot to put up a sign of proof.

Now imagine there is a potential customer who wants to purchase an original LuxWatch. Where do you think this customer will decide to buy it from – the store with visible authorization stating the product is original, or in the store without such authenticity proof?

This logic works the same way for the buying and selling of ad inventory on publishers’ sites. Ad.txt files enable publishers to create an easily accessible public record that declares who is authorized to sell their inventory. This way, potential buyers can be sure the inventory they are buying is actually coming from the original publisher domain they meant to purchase it from.

Ads.txt benefits both the buy-side and the sell-side

The online advertising ecosystem currently suffers from ad fraud due to a lack of transparency, which makes big buyers uncertain about where they should place their ad spend. The ads.txt initiative was introduced to make ad fraud a lot harder to pull off – especially one of the most common forms of fraud, domain spoofing. This occurs when an ad supply provider sells inventory that they claim to be sourced from specific site URLs, but it’s actually coming from a mix of low-quality domains.

Let’s say, for example, that you own the site This site is very popular, and advertisers are willing to pay good rates to serve their ads to your audience. When someone else sells inventory from a different and lower quality site, but makes advertisers think they are buying from, both you and the advertiser are losing. You don’t get the ad revenue that was meant for you, and the advertiser doesn’t reach their intended audience. No one wants to see money go to waste!

Adding the Ads.txt file is essential to make sure that the SSPs can confirm who is, and is not, allowed to sell your inventory; without it, you will miss out on revenue, while setting up the Ads.txt file will give buyers confidence and greater incentive to buy.

How to structure an Ads.txt file

Ads.txt files must provide a comprehensive list of each advertising system that publisher AND that publishers’ partners work directly with, or gave permission to sell inventory on their behalf. Each line in an ads.txt file corresponds to a single demand source, and each line is made up of 4 parts – three mandatory, and one optional:

Part 1: The domain name of the advertising system

Part 2: The publisher’s account ID in the advertising system

Part 3: The type of the relationship between the publisher and the account in the advertising system. If the publisher owns and operates the advertising account itself, it should to be listed as DIRECT. If the account is managed by the publisher’s partner and not directly by the publisher, it should be listed as RESELLER.

Part 4 (optional): The Certification Authority ID. This is an ID that uniquely identifies the advertising system within a certification authority (for example, the Trustworthy Accountability Group, or TAG) and maps to the entity listed in field #1.

Here’s what a line would look like for a publisher that has their own account with Google DoubleClick:, pub-0000000000000000, DIRECT, f08c47fec0942fa0

The final file should be placed under the root domain of the site named /ads.txt. Check out these ads.txt files that have already been published by The New York Times, CNN, and Washington Post.


Milen Debensason