Ads.txt and App-ads.txt Overview

What is ads.txt / app-ads.txt?

Ads.txt (Authorized Digital Sellers) is an IAB initiative designed to increase transparency and prevent unauthorized selling of ad inventory.
It allows publishers to publicly declare which companies are authorized to sell their ad space.

For mobile apps, the same principle applies through app-ads.txt, which works in a similar way but is hosted at the developer’s website listed in the app store.

Here you can read the full IAB description and specification.

How does it work?

For websites (ads.txt): The publisher uploads a simple text file named ads.txt to the root directory of their domain (e.g., https://example.com/ads.txt).
This file lists all authorized advertising partners (such as Clickio and ad exchanges) that can sell the site’s inventory.

For mobile apps (app-ads.txt): App developers host a similar file, app-ads.txt, on their developer website (the one linked in Google Play or App Store).
Ad platforms use this file to confirm that they are authorized to serve ads inside your app.

When programmatic buyers check your domain or developer URL, they verify the connection between you (the publisher or app developer) and the authorized sellers listed in your file. If everything matches, your traffic is marked as verified and trustworthy.

Why is it important for your site or app?

Adding ads.txt (or app-ads.txt) is crucial for proper monetization and buyer trust. Here’s why it matters:

• Transparency: It clearly shows which platforms can sell your ad inventory.
  
• Protection: Prevents unauthorized reselling and domain spoofing.
• Revenue impact: Many demand partners and DSPs buy ads only from verified sources that have a valid ads.txt or app-ads.txt file. Without it, your website or app may be excluded from programmatic auctions, reducing ad revenue.