ConnectAd Chronicles


Why ads.tx and sellers.json are must-haves these days

Programmatic advertising is a type of digital advertising that uses automated systems to buy and sell ad space on website sand mobile apps. This is complicated, raises many questions, and can sometimes be quite opaque. So it's no surprise that programmatic campaigns almost magnetically attract fraudsters. The sad truth is that a huge amount of online advertising dollars go to waste due to bots, click fraud and co.

As we discussed in one of our latest blog posts, this is a big problem for publishers. But advertisers suffer just as much when their ads fizzle out on the web. Fortunately, the appropriate know-how enables us not only to recognize common types of ad fraud, but also to prevent them easily. Two tools that help to increase transparency in general and prevent ad fraud in particular are ads.txt and sellers.json. Today we will take a closer look at them, understand how they work and what they are good for.

Ads.txt: What it is and why publishers need it

 Ads.txt was released by the IAB in may 2017. Back than it used to be a major step to fight ad fraud and create transparency – and it has proven itself until today.

What it is

Ads.txt stands for Authorized Digital Sellers and is a simple, flexible and secure way for publishers and distributors to publicly declare which companies they authorize to sell their digital inventory. This helps advertisers ensure that they are buying ad space from authorized sources, rather than from fraudsters who might be posing as legitimate sellers.

How it works

Ads.txt is a small text file that is integrated into the source code of the page and in which the authorized SSPs and the associated unique IDs of the partners are listed. If the publisher markets his inventory via other channels, these can also be easily taken into account in ads.txt.Since the ads.txt can only be created and modified by the webmaster of a domain, the information in the file is considered valid and authentic. Since the file is hosted on the publisher's root domain, it is also easily accessible to buyers who wish to verify the authenticity of the inventory they are purchasing.

Sounds complicated? No problem, we’ll try to simplify the whole thing a little bit:

Just imagine ads.txt as a list of approved friends that a website owner makes. These friends are companies that are allowed to sell ads on the website. It's like the website owner is saying "these are the people I trust to play with my toys (ads)."

Why it is a must-have

When publishers publicly name their licensed distributors using ads.txt, it makes it more difficult to abuse domain names and provides complete clarity about vendor relationships. The publisher thus has full control over who is allowed to trade their inventory. Should unauthorized intermediaries wish to buy and resell impressions in programmatic trading, this is now only possible with the express permission of the publisher. The SSP can verify the origin and authorization of each impression, identify and block unauthorized resellers.

Ads.txt is nice and all … but not enough!

The fact that ads.txt gives publishers power over their inventory is reason enough for most of them to implement ads.txt. In addition, google and almost all major DSPs today deliver exclusively to sites using ads.txt. Therefore it’s no wonder that according to our experiences 95% of publishers already have a proper ads.txt file in place. And that’s nice but simply not enough. How come? That’s explained quickly: Although ads.txt has been extremely successful by allowing publishers to define who is authorized to sell their digital inventory, it doesn’t make any attempt at revealing the identities of the publisher account IDs within their advertising platforms.

Meet sellers.json: It’s like ads.txt, but for the buy side

In 2019 sellers.json was introduced in order to enable buyers to identify the relationship of their sellers – bringing transparency into the supply chain.

What it is

Sellers.json is a file that provides more detailed information about the companies selling ad space in the programmatic ecosystem. It includes information such as the seller's name, domain, and seller type (e.g. publisher, ad network, or reseller). This helps advertisers to better understand the supply chain and to identify any potential risks associated with the sellers involved in a given transaction.

How it works

Sellers.json is a bit like the SSP’s version of the publisher’s ads.txt file. With sellers.json SSPs basically declare the publishers and inventory providers they are partnered with and whose inventory they have permission to sell. The SSPs host sellers.json as an publicly available file with seller information on their servers and are responsible for managing it. Listed are normally all authorized reseller partners along with their vendor ID and any details about the legal entity that owns the business.

Coming back to our picture with the friends list for the toys (ads):

Sellers.json is like a map that shows how the website owner's toys (ads) are being passed from one friend to another. It's like the website owner is saying "I gave my toy (ad) to this friend, who then gave it to that friend, and so on." This map helps everyone understand who is handling the toys (ads) and make sure they are being passed to the right friends.

Why it is a must-have

Except for shady players who shouldn’t be operating in the first place, sellers.json only brings benefits to all parties involved because it gives a better understanding of the supply-path. As a result everyone can focus more on paths that give the most value for every dollar spent. With better transparency, advertisers just get better ROI and publishers achieve better revenue – it’s as simple as that.

The problem with sellers.json? Setting it up correctly

Similar to the ads.txt initiative sellers.json has been heavily pushed by DSPs, most prominently here The Trade Desk. As a matter of fact DSPs like TTD, Google, or Adform (just to name a few) won’t buy inventory, or will have less appetite, from SSPs, exchanges and online sales houses if they don’t have a correct sellers.json file in place. And here lies the “problem” – even though a sellers.json file is pretty straight forward and simple to set up we do see quite frequently that still too many sales houses have problems with setting it up correctly.

Especially when it comes to the identifiers we have seen quite “creative” solutions to the task. But “creative” just isn’t the way you should choose to go here. Why? Because non-conforming sellers.json files, like for example with not-acknowledged identifier names, can mislead DSPs. As a result these DSPs stop buying this ad inventory which consequently leads to reduced revenue. As matter of fact we have talked to sales houses who have been heavily affected by this issue. Just because their sellers.json file was incorrect they had to forfeit revenue.

It's actually not that difficult

Whether you are new to the whole sellers.json topic or need a little reminder, we frequently see, let's call them creative solutions when it comes to identifiers. The IAB TechLab clearly recommends either of these two standard identifiers that should be used in the identifier list:

1) TAG-ID = Trustworthy Accountability Group ID - this TAG ID is not just any ID but a verified TAG that can be searched and found here.


2) DUNS = Dun & Bradstreet DUNS Number - also clearly identifies the seller as explained here in detail

To sum it up: Overall, ads.txt and sellers.json are must-have tools that help to promote transparency and trust in the programmatic advertising industry by providing a standardized way for buyers to verify the authenticity of the sellers they are working with.

Therefore our tip is to be aware and take all the time you need to set up ads.txt and sellers.json correctly. Those initiatives serve a good purpose and should be taken seriously. At ConnectAd we do so, because transparency is of great significance to us. Therefore feel free to contact us – we are here to help you with obstacles you might face.