Ads.txt

Ads.txt is the Acronym for Authorized Digital Seller

The Authorized Digital Sellers (Ads.txt) initiative is an IAB Technology Laboratory project to prevent ad fraud. It specifies a text file hosted on web servers, listing the companies authorized to sell a publisher’s digital ad inventory. This technology is primarily used in the digital advertising ecosystem to combat ad fraud and ensure transparency in the programmatic advertising supply chain.

rubiconproject.com, 22884, DIRECT, 0bfd66d529a55807
rubiconproject.com, 22884, RESELLER, 0bfd66d529a55807
google.com, pub-5668074111008717, DIRECT, f08c47fec0942fa0
google.com, pub-8571282482737818, RESELLER, f08c47fec0942fa0
adingo.jp, 30898, RESELLER
netpeak.co.uk, 21677305623, DIRECT

Publisher Implementation

Website or app publishers create an ads.txt file, a plain text file, and place it on their web servers. This file lists the names of companies and their associated Publisher IDs authorized to sell their advertising inventory.

Ad Buyer Verification

Advertisers and Demand-Side Platforms (DSPs) use ads.txt files to verify the legitimacy of their buying inventory. When they want to place an ad on a specific website, they check the ads.txt file for that site.

Authorization Check

The ad buyer checks the Publisher ID listed in the ads.txt file against the Publisher ID in the ad placement request. If they match, it’s considered authorized. It raises a red flag and suggests potential fraud if they don’t match.

Fraud Prevention

Ads.txt helps prevent ad fraud, such as domain spoofing, where fraudsters impersonate legitimate websites to sell fake ad inventory. By referencing the ads.txt file, ad buyers can confirm that they deal with authorized sellers.

Ads.txt Explanation

Each line of an ads.txt file follows this structure:

Advertising System Domain: The domain name of the advertising system authorized to sell the app’s ad inventory.
Publisher Account ID: A unique identifier for the publisher’s account within the specified advertising system.
Relationship Type: Specifies the relationship between the advertising system and the publisher. It can be either:
DIRECT: Indicates the advertising system has a direct relationship with the publisher and is authorized to sell their inventory directly.
RESELLER: Indicates the advertising system is authorized to resell the publisher’s inventory, likely through another platform.
Certification Authority ID (Optional): A unique identifier provided by an independent certification authority to further validate the relationship. Its presence adds an extra layer of security.

How Ads.txt Works

App Developer: The app developer creates an ads.txt file and places it on their website’s root domain (e.g., example.com/ads.txt). They link their website to their app store listings.
Advertisers & DSPs: When an advertiser or Demand-Side Platform (DSP) wants to buy ad space in the app, they crawl the app store listings to find the developer’s website and the ads.txt file.
Verification: The advertiser/DSP cross-references the ad requests they receive with the information in the ads.txt file. If the advertising system and publisher account ID in the ad request match an authorized entry in the file, the ad request is considered legitimate. If not, it’s likely fraudulent and can be rejected.