Ads.txt for Publishers

Brock Munro
January 27, 2021
April 23, 2024
Ads.txt for Publishers

Ad fraud is a consistent problem in digital marketing and has shown no indication of settling down. According to eMarketer, ad fraud is estimated to cost the advertising ecosystem over $6.5 billion annually.

For decades, businesses have searched for a variety of ways to solve this costly problem, including looking to blockchain for some insight, but the answer has come via a much simpler solution from IAB Tech Lab, called Ads.txt.

Let’s explore what ads.txt is, how it works and how to implement it.

What is Ads.txt?

Ads.txt is a project created by the IAB Tech Lab and featured by Google in their web ad services AdSense to tackle various types of ad fraud, like domain spoofing and illegal inventory arbitrage, and to ensure transparency in the increasingly ambiguous market.

Launched in May 2017, the ads.txt project is intended to change the web marketing supply chain by making the process easy and simple while protecting inventory for buyers from bad actors.

It allows buyers and authorized sellers in the industry to efficiently buy and sell credible digital advertising services with transparency which will help companies get direct access to the advertising exchange ecosystem and make adoption easy.

In Google Ad Manager, buyers can clearly see whether sellers have valid ads.txt or app-ads.txt files.

Checking valid ads.txt with Google Ad Manager 360

How Does Ads.txt Work?

Now that you know what ads.txt is, let’s dive deeper into how it works.

1. A publisher creates ads.txt files which includes details on all programmatic advertising affiliates, such as supply side channels, ad networks and ad exchanges, where they operate with their site server and administer it under their root domain.

How to Check Sites’ Ads.txt

You can directly search whether a site has ads.txt files and display its files by adding ads.txt to the root domain’s end.

If the publisher has inserted the ads.txt file to their root domain, companies and marketers can utilize a Python script to navigate the site through a server they have built featuring a collection of domains. Through this server, a marketer can identify which publishers have an ads.txt file under their website for sellers’ ads.

2. Once a company or ad exchange has a database of authorized sellers or publishers using ads.txt files, this list can be referenced under publisher ID in OpenRTB offer queries.

If the seller account IDs align, this can serve as a verification of authenticity. If they do not fit or do not apply, it may mean that the website does not come from authorized digital sellers or that the seller is not authorized to sell ads.txt, and that the customers may opt not to transact for that specific inventory.

Ads.txt is an impactful strategy for countering domain spoofing when the publisher is the sole entity that can apply an ads.txt file to their website. This ensures that the ads.txt file cannot be updated by another platform and then used to sell counterfeit inventory.

What Problem Does Ads.txt Solve?

In addition, ads.txt attempts to fix domain spoofing, which is not technically ad fraud but is still a dubious practice.

Arbitrage is a practice where impressions are purchased and then reconfigured and sold back at a cheaper rate by an external entity. Ads.txt tries to overcome this issue by identifying which are the approved suppliers of the publisher’s inventory.
Domain spoofing operates in two forms, either by utilizing malware that has been placed on a consumer’s device or by modifying an ad tag’s URL.

Both approaches yield the same effect as they deceive ad exchanges and other data-driven websites into believing that the consumer is accessing a genuine platform while the ad either appears on a separate, illegal site or is viewed on a website in a covert web application.

The reason why this unethical activity has persisted for such a long time is because it is tough for publishers in the industry to ensure that the details in the text file about their inventory look like they are accurate.

Now, with ads.txt, domain spoofing and sales of counterfeit inventory have become a lot more challenging. Sellers who have not had their ads.txt verified will be blocked from serving unauthorized ads.

Problems ads.txt solves

Benefits for Publishers

Now let’s take a look at the benefits of ads.txt for publishers. Authorized digital sellers can openly display approved retailers of their ad inventory, while having ads.txt can avoid illegitimate incidents of fraudulent purchases of inventories.

Ads.txt also helps ad buyers to verify dealers and thereby prevent unwanted traffic transactions. The service also assists mobile advertisers through app-ads.txt. This software generates a unified namespace using the developer URL, which will help consumers detect and prevent occurrences of unwanted imitations, while redirecting precious advertisement budget back to publishers.

How to Create and Implement Ads.txt

1. First, get all the details you need from your profiles with vendors, network affiliates, and groups who make your inventory open to customers. This involves the domain name of the advertisement network, Publisher ID, whether the account is direct or reseller and more.

2. Make an ads.txt file in a word document creation software that is compatible with the IAB. Archive and mark the ads.txt file.

3. Next, attach the document to the root of the domain.

Note that since subdomains are not applicable, they will not work so only use the root. This will help you connect with authorized digital sellers and websites authorized to sell their inventory.

An example of an ads.txt file

Is Ads.txt Still Being Adopted by Publishers?

Recent findings indicated that the ads.txt initiative was not implemented at the pace most anticipated, provided that it is a reasonably simple method which removes one of the main advertisement and technology issues.

Nevertheless, since its introduction in May 2017, it has become almost mandatory for publishers to implement ads.txt if they want to sell their inventory programmatically. To make the most of the process, publishers should ensure they keep their ads.txt file up to date while keeping an eye on which sellers have been authorized to sell their inventory.

Apps-Ads.txt for Mobile Apps

After its arrival in May 2017, ads.txt has progressively been accepted by businesses in the AdTech field, rendering it far more challenging for scammers to manipulate domains. Even so, there is yet another form of advertisement fraud that is prevalent in the business world, mobile app fraud.

The original publication of the IAB’s guidelines for the introduction of ads.txt did not allow for adequate steps to deter mobile app fraud. As a result, app-ads.txt was developed to provide the same functionality that ads.txt was providing for web users.

In June 2018, the IAB Tech Lab posted an overhaul of the recommendations and made them open for users to give feedback on for a month. In August 2019, Google Ad Manager and AdMob implemented a feature which allowed clients with app-ads.txt to block unauthorized ad inventories.


How do I create an ads.txt file on my website?

Upload your ads.txt file to your website’s root directory. The root directory of the web is the folder that follows the top level domain.

Check if you have correctly accessed the contents of your file when you enter advertisements to confirm that you have submitted your file accurately.

Are ads.txt files mandatory?

Use of ads.txt is not compulsory, but is strongly advised. It can help safeguard your company from counterfeit inventory that’s intentionally mislabelled as originating from a specific domain, app, or video.

Wrap Up

To wrap up, let’s go over the main functions of ads.txt. It establishes a text file that companies can host on their web servers, and makes a list of the companies authorized to sell their products or services.

This allows companies to evaluate the performance of their inventory, ensure only authorized sellers can access their website, and safeguard against internet fraud.

As you can see, ads.txt is an integral part of the online advertising world. Be sure to adopt this innovative technology if you haven’t already.

If you’re making more than $2,000 in monthly ad revenue, contact us today to learn more about how Publift can help increase your ad revenue and best optimize the ad space available on your website or app.

Grow with us

Grow your business with a sustainable, long term partnership. If you're making more than $2,000 in monthly ad revenue, contact us today to boost your revenue with our all-in-one solution.
Laptop screen with web page open

Success Stories