Fake impressions and fraudulent clicks are a huge problem for publishers and advertisers. You probably already know about ads.txt, a system that helps buyers and sellers run a fair and transparent deals in programmatic advertising. Ads.cert is phase two in the same direction.

IAB (Interactive Advertising Bureau) introduced ads.cert stating, “The combined use of the proposed OpenRTB 3.0 tech spec in conjunction with ads.cert, AdCOM, and the Ad Management API, will improve security and support new use cases in OpenRTB on both the buy and sell sides, ultimately facilitating a better consumer experience.”

In short, ads.cert is here to bring transparency and fairness in the programmatic advertising industry.

What is Ads.cert?

The role of ads.cert is to authenticate the exchange between buyer and seller at each stage of digital ad supply chain, ensuring no information is modified or altered.

IAB introduced ads.cert to complement ads.txt. It will be wrong to say that ads.cert is an update of ads.txt. Because ads.txt is doing what it was designed to do (address domain fraud). However, using ads.cert with ads.txt should bring comprehensive security against ad fraud.

As per reports, one in every five websites is visited by fraudulent bots. Ads.cert will help validate that the impression received on an ad is really from the intended publisher’s website. Fake impressions happen because fraudsters can manipulate ad variables anywhere down the ad supply chain. Ads.cert is intended to stop this from happening.

How Does Ads.cert Work?

Ads.cert uses cryptographically-signed bid requests to verify and validate the inventory. It starts with the publisher generating two encrypted keys—public key and private key. The public key is visible to everyone and available on the publisher’s website. And the private key is only for publisher containing authentication details of the inventory.

Before making a deal, publisher shares the private key with the SSP. Using this private key, SSP creates bid requests and attach the private key signature with each request. This signature contains the details of the inventory (available impression, website details, supporting format and more). On the buyer side, the DSP matches the public key with the private key. If both the value match, DSP will know that the inventory is authentic and unmodified.

Ads.cert is only supported by OpenRTB 3.0. OpenRTB 3.0 is designed by IAB to enforce new programmatic buying techniques. However, OpenRTB 3.0 is not backward compatible. Meaning, it doesn’t support the older versions. And in order to update to the newer technology, DSP and SSP will have to pay a significant amount in engineering costs.

Why do we Need Ads.cert?

Publishers add a text file (ads.txt) to their website containing a list of all sellers and resellers of their ad inventory. This method effectively fights against domain spoofing.

But there were some problems that ads.txt failed to resolve. Ads.txt doesn’t specify the inventory type. Meaning, display inventory can be repackaged and sold as video, and therefore artificially inflate CPMs for publishers. Also, the creation and insertion of ads.txt file is a manual process. Due to human error, any information uploaded can be wrong.

Here’s how ads.cert can help advertisers and publishers:

Ads.cert Benefits for Advertisers

  • Advertisers can identify authorized inventories
  • Advertisers ad will not be displayed on fraudulent sites
  • Promotes true impressions which result in better revenue generation

Ads.cert Benefits for Publishers

  • Ads.cert blacklists fake inventory which creates an opportunity for genuine publishers
  • Due to the authentication, publishers can sell inventory at a better price
  • Creates an authentic and transparent environment for programmatic advertising

How are Ads.txt and Ads.cert Related?

Marketers often get confused between ads.cert and ads.txt. Some say that ads.cert is an update to ads.txt technology. But this is not true. Ads.txt and ads.cert go hand in hand.

Ads.txt authenticates the seller and ads.cert authenticate the inventory.

Suppose, you went to purchase a pair of Adidas shoes. First, you need to find an Adidas seller. Next, you’ll look for a pair of shoe that fits you. For that, you would like to know size, colour, print, and other details. Once you are satisfied, you will make the purchase.

Similarly, digital inventory buyer will start by making sure that the seller has authority to sell the inventory. This is achieved by ads.txt. After that, the buyer will look for types of inventories on sale. If the inventory is authentic and satisfies the requirement, the buyer will purchase it.


We learned that ads.txt and ads.cert work together to provide transparent programmatic buying. Both sellers and buyers need to go along with the rules of the ads.txt and ads.cert to bring fairness to the industry. However, the success of this method depends on industry adoption. Ads.cert brings some solutions on the table. But the fight against ad fraud fight isn’t over yet.


Shubham is a digital marketer with rich experience working in the advertisement technology industry. He has vast experience in the programmatic industry, driving business strategy and scaling functions including but not limited to growth and marketing, Operations, process optimization, and Sales.

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