How to Fix Ads.txt Error?

Last Updated on 19th May 2023 by Ajmer Singh

In the digital advertising landscape, transparency and trust are paramount.

Publishers and website owners face the challenge of ensuring that their inventory is sold through authorized channels, preventing unauthorized sellers from misrepresenting their ad space.

To address this issue, the Interactive Advertising Bureau (IAB) introduced ads.txt (Authorized Digital Sellers), a text file that allows publishers to declare the authorized sellers of their digital ad inventory.

However, implementing and maintaining an ads.txt file can sometimes be daunting, as errors and inconsistencies can arise.

This article aims to provide a comprehensive guide on how to fix ads.txt errors, understand its purpose, troubleshoot persistent issues, verify successful implementation, and establish best practices for maintenance.

By following these guidelines, publishers can enhance transparency, protect their inventory, and build a more trustworthy programmatic advertising ecosystem.

Ads.txt Errors: A Comparison Chart

When it comes to resolving ads.txt errors, having a clear and systematic approach can save publishers valuable time and ensure a smooth implementation.

This chart presents a step-by-step guide to fixing ads.txt errors, providing a concise overview of each essential step.

From verifying the file location to updating the ads.txt file and refreshing the website, these steps cover the crucial actions needed to address common issues.

By following this guide, publishers can navigate through the process effectively, resolve errors, and maintain an accurate and reliable ads.txt file, promoting transparency and trust in their programmatic advertising endeavours.

Steps Description
1. Verify ads.txt file location Check if the file is in the correct directory
2. Check syntax and format Ensure proper formatting, commas, and field arrangement
3. Resolve syntax errors and typos Correct any misspelled domains or incorrect seller IDs
4. Validate domain ownership Confirm authorization and ownership of the listed domains
5. Update the ads.txt file Make necessary changes and additions to authorized sellers
6. Clear cache and refresh website Clear cache to reflect updated ads.txt file on the website

Introduction to ads.txt Error

understand ads.txt error

Ads.txt (Authorized Digital Sellers) is an IAB (Interactive Advertising Bureau) initiative that helps publishers protect their inventory from fraudulent activities by specifying authorized sellers of their ad space.

It is a simple text file that is placed on a publisher’s website and contains a list of authorized sellers along with their identifiers.

However, despite its simplicity, errors can occur in the implementation of ads.txt, leading to ads.txt errors.

When an ads.txt error occurs, it means that there is an issue with the ads.txt file on a publisher’s website, preventing the proper authorization of sellers and potentially causing disruptions in ad serving or revenue loss.

These errors can occur due to various reasons, ranging from syntax errors and typos to more complex issues related to server configurations or CMS limitations.

Let’s take a look at a couple of examples to illustrate ads.txt errors:

Syntax Error:

One common ads.txt error is a syntax error, where the formatting or structure of the ads.txt file is incorrect.

For example, if a line in the file is missing a required field or contains an extra space or character, it can result in an ads.txt error.

Here’s an example of a syntax error:,123456789, DIRECT,

In this case, the fourth field “” is not a valid domain or seller ID, causing an error.

Fixing this error would involve identifying the correct domain or seller ID and correcting it in the ads.txt file.

Authorization Error:

Another type of ads.txt error can occur when the authorization of sellers is not properly set up, resulting in unauthorized sellers being able to serve ads on a publisher’s website.

This can happen if the authorized sellers’ identifiers are not correctly specified in the ads.txt file. Here’s an example:,123456789, DIRECT

In this example, the seller ID or account ID is missing, leading to an ads.txt error. To fix this, the correct seller ID or account ID must be added to the file.

These are just a couple of examples of ads.txt errors that publishers may encounter.

It’s important to understand these errors and how to fix them to ensure the proper functioning of ads.txt and prevent unauthorized ad serving on your website.

In the following sections of this article, we will explore the common causes of ads.txt errors and provide a step-by-step guide to fixing them.

Understanding the Purpose of ads.txt

faqs about ads.txt error

The purpose of ads.txt (Authorized Digital Sellers) is to combat ad fraud and protect the inventory of publishers by establishing a transparent and trusted ecosystem for programmatic advertising.

By implementing ads.txt, publishers can declare the authorized sellers or resellers who are permitted to sell their ad inventory, thus reducing the risk of unauthorized or fraudulent ad placements.

Here are a couple of examples to help understand the purpose of ads.txt:

Preventing Domain Spoofing:

One of the primary purposes of ads.txt is to prevent domain spoofing, a type of ad fraud where unauthorized entities misrepresent themselves as legitimate publishers.

These fraudulent actors may create counterfeit websites or mimic the domains of reputable publishers to deceive advertisers and gain access to ad budgets.

By using ads.txt, publishers can explicitly list the authorized sellers or ad networks that have permission to sell their inventory.

Advertisers can then verify the authenticity of the sellers by cross-referencing the information in the ads.txt file with the actual programmatic transactions.

This transparency helps prevent domain spoofing and ensures that advertisers are dealing with legitimate publishers.

Increasing Transparency and Trust:

Ads.txt aims to increase transparency in the programmatic advertising ecosystem.

It provides a public record of authorized sellers, their corresponding account IDs, and the relationships between publishers and sellers.

This information can be accessed by advertisers, agencies, and ad networks to verify the legitimacy of the inventory they are purchasing.

For example, an advertiser can check the ads.txt file of a publisher’s website to confirm that the seller from whom they are buying ad space is authorized.

This verification process builds trust and reduces the risk of spending advertising budgets on fraudulent or low-quality inventory.

Also, ads.txt helps in identifying and mitigating unauthorized reselling of inventory.

Publishers can specify their authorized resellers in the ads.txt file, ensuring that only trusted entities are involved in reselling their ad inventory.

Common Causes of ads.txt Errors

prevent ads.txt error

While implementing and maintaining ads.txt, publishers may encounter various errors that can disrupt the proper functioning of the file.

Understanding the common causes of ads.txt errors is essential for troubleshooting and resolving these issues. Here are a few examples of common causes:

Syntax Errors:

Syntax errors occur when the formatting or structure of the ads.txt file is incorrect.

These errors can include missing fields, extra spaces, or invalid characters. For instance:,123456789, DIRECT,

In this example, “” is not a valid domain or seller ID, resulting in a syntax error.

Resolving this error involves identifying the correct domain or seller ID and correcting it in the ads.txt file.

Typos and Misspellings:

Typos and misspellings can lead to ads.txt errors, preventing the proper authorization of sellers. For example:,123456789, DIRECT,

In this case, “” contains a typo and should be “”

Fixing this error requires correcting the misspelled domain in the ads.txt file.

Incorrect Seller ID or Account ID:

An ads.txt error may occur if the seller ID or account ID is missing or incorrect. Here’s an example:, , DIRECT,

In this instance, the seller ID or account ID field is empty, causing an error.

To fix this, the correct seller ID or account ID should be added to the ads.txt file.

Server Configuration Issues:

Issues with server configurations can result in ads.txt errors.

For instance, if the ads.txt file is not placed in the correct directory on the server or if the server permissions are not set correctly, the file may not be accessible to ad networks or other parties.

Verifying the file location and ensuring proper server configurations can help resolve these errors.

Incomplete or Outdated ads.txt Files:

If the ads.txt file is incomplete or outdated, it can lead to errors.

For example, if the file is missing authorized seller information or fails to include the latest changes in seller authorizations, it may result in an ads.txt error.

Regularly reviewing and updating the ads.txt file is crucial to prevent these errors.

Identifying ads.txt Error Messages

fix ads.txt error

When encountering ads.txt errors, it’s crucial to identify the specific error messages or indications that can help pinpoint the issue.

Understanding these error messages can assist in troubleshooting and resolving ads.txt errors.

Here are a few examples of common error messages and their meanings:

“File Not Found” or “404 Error”:

If you encounter a “File Not Found” or “404 Error” message when attempting to access the ads.txt file through its URL (e.g.,, it indicates that the file is missing or cannot be located on the server.

This error suggests that the file may not be properly uploaded or named incorrectly.

Ensure that the file is in the correct location and has the appropriate file name (ads.txt) for easy accessibility.

“Incorrect File Permissions”:

If you receive an error message related to incorrect file permissions, it suggests that the server does not allow the necessary access to the ads.txt file.

This error commonly occurs when the file permissions are set to restrict public access.

Adjusting the file permissions to allow public read access (e.g., 644 or similar) should resolve this issue.

“Syntax Error” or “Malformed ads.txt”:

A “Syntax Error” or “Malformed ads.txt” message indicates that there is an issue with the structure or formatting of the ads.txt file.

It may result from missing or incorrect fields, improper line breaks, or invalid characters.

Carefully review the ads.txt file and ensure that it adheres to the correct syntax, following the guidelines provided by the IAB.

Correct any syntax errors to resolve this issue.

“Invalid Seller ID” or “Unrecognized Seller”:

If you encounter an error message indicating an invalid seller ID or unrecognized seller, it implies that the seller identifier specified in the ads.txt file is incorrect or not recognized.

Check the seller ID provided in the file and cross-reference it with the authorized seller information.

Ensure that the correct seller ID or account ID is used for authorized sellers.

“Missing Field(s)”:

A “Missing Field(s)” error message suggests that one or more required fields in the ads.txt file are missing.

The ads.txt file should include four fields in each line: the domain, the seller ID, the relationship type, and the certification authority ID (optional).

Check that all the required fields are present and correctly filled in each line of the ads.txt file.

“Duplicate Entries”:

An error message regarding duplicate entries indicates that the ads.txt file contains multiple lines with the same domain and seller ID combination.

Duplicate entries can cause conflicts and may result in an error.

Remove the duplicate entries from the ads.txt file to ensure each combination of domain and seller ID appears only once.

“Domain Not Authorized”:

If you receive a “Domain Not Authorized” error message, it suggests that the specified domain is not authorized to sell the inventory specified in the ads.txt file.

Verify that the domain listed in the file matches the actual domain of the publisher and ensure that the authorized sellers are accurately declared.

Step-by-Step Guide to Fixing ads.txt Errors 

fix ads.txt error

Verifying the ads.txt File Location:

Confirm the location of the ads.txt file on your server.

It should be placed in the root directory of your website (e.g.,

Ensure that the file is named correctly as “ads.txt” and is accessible through its URL.

Checking the Syntax and Format of the ads.txt File:

Open the ads.txt file using a text editor or a code editor.

Verify that each line follows the correct syntax: domain, seller ID, relationship type, and optionally, the certification authority ID.

Example:,123456789, DIRECT,

Resolving Syntax Errors and Typos:

Review each line of the ads.txt file and check for syntax errors or typos.

Ensure that there are no missing fields, extra spaces, or invalid characters.

Example:,123456789, DIRECT,

Correction:,123456789, DIRECT,

Validating the Domain Ownership and Authorization:

Confirm that the domain listed in the ads.txt file matches the actual domain of the publisher.

Validate the authorized sellers by cross-referencing their seller IDs with the information provided by the ad networks or exchanges.,123456789, DIRECT,

Ensure that “” is an authorized seller with the correct seller ID.

Updating the ads.txt File on the Server:

Make any necessary corrections to the ads.txt file on your local machine.
Upload the updated file to the correct location on your server, typically the root directory.

Replace the existing ads.txt file with the updated version.

Clearing Cache and Refreshing the Website:

Clear your browser cache to ensure you are viewing the most recent version of the website.

Refresh the website to fetch the updated ads.txt file.

Verifying Successful ads.txt Implementation

identify ads.txt error

Once you have made the necessary fixes to your ads.txt file and updated it on the server, it’s important to verify that the implementation was successful.

Here are some steps to help you ensure that ads.txt is properly implemented:

Accessing the ads.txt File:

Open a web browser and navigate to your website’s root domain (e.g.,

Append “/ads.txt” to the URL (e.g.,

Verify that the browser displays the content of the ads.txt file without any error messages.

Checking for Correct Syntax and Format:

Review the contents of the ads.txt file displayed in the browser.

Ensure that each line follows the correct syntax and format: domain, seller ID, relationship type, and optionally, the certification authority ID.

Example:,123456789, DIRECT,

Verifying Authorized Sellers:

Cross-reference the information in the ads.txt file with the list of authorized sellers or resellers provided by your ad networks or exchanges.

Ensure that the seller IDs and domains listed in the ads.txt file match the authorized entities.

Testing ad serving:

Visit various pages on your website where ads are expected to be displayed.

Check if ads are being served correctly and from the authorized sellers specified in the ads.txt file.

Make sure that the ads are not being blocked or showing any error messages.

Validating through Ad Network or Exchange Tools:

Some ad networks or exchanges provide tools or verification mechanisms to validate the implementation of ads.txt.

Check if your ad network or exchange offers such tools and use them to confirm that the ads.txt file is correctly implemented.

Troubleshooting Persistent ads.txt Errors 

troubleshooting ads txt errors

Sometimes, you may encounter persistent ads.txt errors that are challenging to resolve.

In such cases, it’s important to dig deeper and explore potential underlying issues.

Here are some troubleshooting steps to address persistent ads.txt errors:

Checking Server Permissions and File Accessibility:

Ensure that the ads.txt file has the correct file permissions set on the server.

It should have read access for the public (e.g., 644 or similar permissions).

Confirm that the file is located in the correct directory and accessible through its URL.

Example: Use the command line or a file manager to verify the file permissions on your server.

Double-check the file location and URL (e.g.,

Resolving CDN and Caching Issues:

If you use a Content Delivery Network (CDN) or caching system, it’s possible that the ads.txt file is being cached, leading to errors.

Configure your CDN or caching system to exclude the ads.txt file from caching or implement cache-busting techniques.

Example: Consult the documentation or support resources of your CDN or caching system to learn how to exclude specific files from caching.

Implement cache-busting techniques such as appending version numbers or timestamps to the ads.txt file URL to ensure it is always fetched fresh.

Addressing CMS or Website Platform Limitations:

Some Content Management Systems (CMS) or website platforms have limitations or specific configurations that can interfere with ads.txt implementation.

Consult the documentation or support resources of your CMS or website platform to understand any specific requirements or limitations related to ads.txt.

Example: If your CMS automatically generates the ads.txt file, ensure that the generated file follows the correct syntax and is updated with the authorized seller information.

Verify if there are any plugins or extensions available that facilitate proper ads.txt implementation within your CMS or website platform.

Best Practices for ads.txt Maintenance

ads txt maintenance

To ensure the effectiveness and accuracy of your ads.txt file, it’s important to follow best practices for its ongoing maintenance.

Here are some key practices to consider:

Regularly Reviewing and Updating ads.txt Files:

Set a schedule to periodically review your ads.txt file, especially when changes occur in your authorized sellers or resellers.

Update the file promptly to reflect any changes, additions, or removals of authorized sellers.

Example: Conduct a monthly or quarterly review of your ads.txt file to ensure it aligns with your current partnerships and authorized sellers.

Add or remove seller entries based on any changes in your business relationships or authorized sellers.

Monitoring Changes in Authorized Sellers:

Stay informed about changes in your authorized sellers by maintaining effective communication channels with your ad networks, exchanges, and partners.

Regularly review updates or notifications provided by your ad partners regarding changes in seller IDs, domains, or authorized resellers.

Example: Stay updated with newsletters, email notifications, or announcements from your ad partners to be aware of any changes to authorized sellers.

Maintain open communication with your ad partners to promptly address any changes or updates to the list of authorized sellers.

Ensuring Compliance with Ad Exchange Requirements:

Ad exchanges may have specific requirements for ads.txt implementation. Familiarize yourself with their guidelines and ensure compliance.

Stay up to date with any changes or updates to the guidelines provided by the Interactive Advertising Bureau (IAB) regarding ads.txt.

Example: Regularly visit the IAB website or subscribe to their updates to stay informed about any changes to ads.txt specifications.

Follow the guidelines provided by ad exchanges and ensure your ads.txt file meets their requirements to maximize compatibility and transparency.

Preventing ads.txt Errors in the Future

prevent ads txt errors

To minimize the occurrence of ads.txt errors and ensure a smooth implementation, it’s important to focus on preventive measures.

Here are some practices to help prevent ads.txt errors in the future:

Educating Team Members and Stakeholders:

Provide comprehensive training and education to your team members and stakeholders involved in managing and implementing ads.txt.

Ensure they understand the purpose of ads.txt, its syntax, and the importance of keeping it up to date.

Example:Conduct workshops or training sessions to educate team members about the significance of ads.txt and how to correctly update and manage it.

Share resources, guidelines, and best practices to enhance their understanding of ads.txt implementation.

Automating ads.txt Verification and Updates:

Explore automation tools or scripts that can verify the integrity of your ads.txt file and detect potential errors or inconsistencies.

Implement automated processes to regularly update the ads.txt file based on changes in authorized sellers or resellers.

Example:Utilize scripts or tools that automatically check the syntax, format, and validity of the ads.txt file, reducing the likelihood of human errors.

Use APIs or data feeds provided by your ad partners to automatically update the ads.txt file based on changes in authorized sellers.

Implementing Proper Change Management Processes:

Establish well-defined change management processes to ensure smooth and controlled updates to the ads.txt file.

Maintain proper documentation and version control to track changes, approvals, and the history of updates made to the ads.txt file.

Example: Implement a change management system or process that includes proper approvals, testing, and documentation for any changes made to the ads.txt file.

Keep a record of each version of the ads.txt file and the corresponding changes made, making it easier to identify and revert any erroneous updates.


avoid ads txt errors

In conclusion, understanding how to fix ads.txt errors and maintaining a healthy ads.txt file is crucial for publishers and website owners in the programmatic advertising ecosystem.

By following the step-by-step guide to fixing ads.txt errors, publishers can resolve common issues such as file location, syntax errors, and validation problems.

Verifying successful ads.txt implementation ensures that the file is correctly implemented and authorized sellers are accurately reflected.

However, troubleshooting persistent ads.txt errors may require additional steps such as checking server permissions, addressing CDN and caching issues, and considering CMS or website platform limitations.

By adopting best practices for ads.txt maintenance, including regular review and updates, monitoring changes in authorized sellers, and ensuring compliance with ad exchange requirements, publishers can maintain an accurate and up-to-date ads.txt file.

Preventing future ads.txt errors involves educating team members and stakeholders about ads.txt, automating verification and updates, and implementing proper change management processes.

These measures help minimize errors, improve efficiency, and enhance transparency within the programmatic advertising ecosystem.

By actively maintaining and monitoring the ads.txt file, publishers can protect their inventory from unauthorized sellers, reduce the risk of fraudulent activity, and foster a more trusted and transparent advertising environment.