Ads.txt: How to Create, Update and Implement Ads.txt

Ads.txt: How to Create, Update and Implement Ads.txt

The online advertising industry has faced widespread ad fraud for years, leading to lost revenue and frustration for publishers and advertisers. In 2019, about 20% of American ad impressions were fraudulent. With sophisticated ad fraud and bots threatening the digital advertising ecosystem, publishers have been scurrying to tackle transparency issues in the ads marketplace. 

The introduction of Ads.txt or Authorized Digital sellers file provides transparency and safety and ensures all clicks and impressions are genuine. Here’s what you need to know about ads.txt and how to implement it on your website.

Brief History of Ads.txt

Cybercriminals carry out ad frauds using fake botnets that mimic human behavior and help generate thousands of counterfeit clicks and visits to sites displaying ads. In addition, domain spoofing allows pirate sites, bot-driven websites, and sites with dubious content to monetize sites otherwise excluded from advertisers or blacklisted by changing the ad tags. 

These methods of ad fraud deceive ad exchanges and other platforms into believing the user is visiting a legitimate site when the ad appears on a separate, illegal site.

CNBC reported that advertisers lost $16.4 billion in revenue in 2017 compared to $12.5 billion the previous year. However, due to organizations like the International Advertising Board (IAB) in the spring of 2017, the IAB Tech Lab introduced Ads.txt to help publishers and buyers fight fraud in programmatic advertising.

What Is Ads.txt?

Ads.txt or Authorized Digital Sellers text file is a list of all partners, including publishers authorized to sell your inventory. It ensures that the ad inventory displayed on publisher websites across any ad exchange is legitimate

Ads.text was initially intended only for online advertising, but now it is also used for mobile apps such as streaming services. The equivalent of Ads.txt files for these streaming services is called app ads.txt. It adds support for mobile app ads and ensures the ad inventory is only sold through authorized channels.

Need of Ads.txt for Publishers and the Advertising Industry

Ads.txt files protect publishers from unauthorized inventory sales and let advertisers check the seller to stop suspicious transactions. For the advertising industry, these files offer transparency in a brand-safe environment.

Increased Transparency

When an advertiser accesses an Ads.txt file and sees that another company has listed their domain as an authorized seller for that specific website, they know there’s no chance it could be fraudulent or unsafe for them to purchase ads from that source. This transparency helps prevent bad actors from selling fake inventory through a publisher’s site without their knowledge and consent.

Ensure Brand Safety in Advertising

Brand safety refers to instances when ads end up on inappropriate websites due to the lack of transparency. Ads.txt helps address these issues by providing a way for advertisers to understand which companies are authorized sellers of ad inventory on a given domain name. It also helps ensure that ads are only displayed on reputable sites and protects brands from inadvertently associating themselves with objectionable content.

Enhances Mobile Advertising

Advertisers always look for ways to reach their target audiences and make the most of their advertising budget. App ads.txt lets advertisers and publishers have more reliable and safer options for reaching mobile audiences. In addition, publishers can control who can sell ads in their apps with the app-ads.txt file.

Benefits of Ads.txt

Creating an Ads.txt File requires little technical skill and knowledge. Publishers can easily create and install Ads.text files on their sites.

Creating an Ads.txt file is Easy

Ads.txt files are easy to create and only take a few steps to upload to a website. This file is saved as a text file and uploaded into the root domain with all the authorized sellers.

Straightforward Updates to Ad.txt files

If a publisher has access to the root domain, they can easily alter and update the Ads.txt file. All they need to do is create a new file with the .txt extension with the updated information and make sure the new.txt file replaces the old.txt.

Secure Access to the Website

Publishers are the only people who can upload Ads.txt files to their websites. This private access ensures no cybercriminals can edit or corrupt the file unless they have the proper credentials to enter the site. They also can’t trick advertisers into selling fake ad inventory.

How Does Ads.txt Work?

Publishers install the Ads.txt file on their websites, confirming their ownership of the domains. They also signal the partner accounts, including ad networks and other publishers, to sell their ad inventory. As a result, advertisers can easily view the authorized partners and their ad inventories. 

An advertiser needs to match the publisher ID with the Ads.txt when they receive a bid request from the publisher. If the publisher ID and the Ads.txt match, the advertiser can trust the publisher. If publishers and ad networks have adopted ads.txt, buyers can check ad tags to verify their authenticity. Conversely, when the publisher ID is invalid, the advertiser can choose not to bid on the publisher’s ads.

How to Create and Implement Ads.txt?

A publisher can create an Ads.Txt file using any text editor such as Notepad and Microsoft Word. The IAB Tech Lab specifies that ads.txt files must be formatted with commas between all the lines. Each line in the Ads.txt file should contain the following:

  • Domain Name

    Publishers must include the canonical domain, or the preferred domain, that will sell the ad inventory. It establishes the domain’s ownership for advertisers. The canonical domain is important, especially if the publishers use multiple domains to sell ads. For example, a domain name must be for seller accounts in Google.

  • Publisher/Account ID

    This line represents the unique publisher ID for advertisers to verify the publishers. Publishers can also obtain their publisher IDs through Google Adsense. For example, the publisher ID appears as pub-0000000000000000.

  • Type of Relationship

    Advertisers can know if a publisher is authorized to sell directly or through another party. This line indicates whether the relationship is DIRECT or RESELLER. The DIRECT value means publishers have entered into a direct contract with an ad network. A RESELLER value refers to the publisher authorizing a third party to sell ad space through the domains indicated in the first line on its behalf.

  • Certification Authority ID

    Some advertising networks are verified. Publishers must add the certification authority IDs. Advertisers can use the certification authority ID to identify an ad network within that authority. The Trustworthy Accountability Group (TAG) acts as the certification authority, and the TAGID acts as the ID. For example, a TAG Id can look like this f08c47fec0942fa0.

How to Upload Your Ads.txt File

Once the publisher puts the file together, they can upload it to the site. They can upload Ads.txt files to the domain’s root using FTP or a file manager. Additionally, many web hosts use file managers to deploy Ads.txt files. Upon uploading it to the domain’s root, the file should show as

How to Set Up Ads.txt

Publishers can set up Ads.txt files through WordPress, Google AdSense, or Google Ad Manager. They must go through a different process to upload the files if they have mobile apps.


Various free plugins that manage Ads.txt files are the easiest way to set up Ads.txt in WordPress.

  • Install the ads.txt plugin on your WordPress website.
  • Click on Settings > Ads.txt in the left panel to customize the settings.
  • Add the Ads.txt file and save the settings.

If there is no need for a plugin, a publisher can navigate to the Media tab in the menu. Choose the Add New Button and upload the Ads.txt file there.

Google AdSense

The publisher must first sign in to the Google AdSense account to start uploading the file. From there, they can take the following steps:

  • Click on Sites and go to the downward arrow. This will open the message to create an ads.txt file.
  • Choose the Download button. The Ads.txt is automatically downloaded.
  • Place your ads.txt file in the root directory of your website.

Publishers can check if the upload was successful in their web browser by typing the ads.txt URL such as

Google Ad Manager

Accessing the Ads.txt manager in Google Ad manager requires having at least one connected Ad Exchange account and allowing a user to manage the Ads.txt file.

  • Select the Web ads.txt tab from the Ads.txt management menu, and then choose to Create an ads.txt file.
  • A dialog window will pop up for the user to verify the file and its lines.
  • Two options are available to set up the Ads.txt file: Copy the text to the clipboard before pasting it into your own ads.txt or download the file.
  • The user can then upload the file into the domain.

Mobile Apps

Uploading an Ads.txt file for a mobile app is similar to setting one up for a website. However, the publisher must create a developer website first to educate customers about their apps and other content. Then, the website must connect to a listing in an app store like Google Play Store, App Store for Android, Apple Store, and other ad networks to prove an app’s ownership.

The publisher can then upload the Ads.txt file to the developer website’s root domain. Verify that the domain matches what appears in the app store. Firebase Hosting is one of the options that Google recommends if your website does not support the publishing of app-ads.txt.


  • Are Ads.txt files mandatory?

    Google recommends adding an Ads.txt file, but it is not mandatory. However, publishers can benefit from having an ads.txt file by stopping counterfeit inventory purchases and ensuring the ad inventory is valid.

  • How do I fix an Ads.txt file?

    If you have incorrect information in the original file, you can replace it by downloading it and making your changes. It is essential to include all the information, including the domain name, publisher ID, and account relationship. Once you’ve modified the file, save and upload it.

  • How do I verify an Ads.txt file?

    Online ads.txt validators offer the most straightforward method for validating ads.txt files. Insert the ads.txt URL into the validator to verify the publisher ID, the domain, and all fields are complete.

  • In what ways does Google enforce Ads.txt files if I use them?

    Google can decide which publishers can show ads using the Ads.txt files in the domain. Then, the company can run an auction for ads on sites with Ads.txt files and the correct publisher IDs. There’s no auction if the publisher ID in the file is incorrect.

  • Can Ads.txt files be on a subdomain?

    Google can search and implement Ad.txt files in subdomains when there is a line for subdomains in the files.

    You add a subdomain= declaration to the ads.txt file if you want to reference a subdomain. For instance, if your ads.txt file for has to include the subdomain, you would write in your ads.txt.

  • Do I need to update my Ads.txt file if I implement header bidding?

    You may need to change your file if you also use header bidding to attract advertisers. This is because the Ads.txt file must have frequent updates when you need to add new partners to your list.

Get Expert Advice from CodeFuel

All publishers who want to monetize their websites must include Ads.txt files to show their validity to potential advertisers. Having these files can assure advertisers that their ads can be promoted in a safe environment with total transparency and combat ad fraud. 

You can work with CodeFuel to understand how Ads.txt files can work for your site. When you work with CodeFuel, you can learn how to prevent potential ad fraud and reduce losses in your financial revenue.