What means every part of one line in ads.txt file?

April 12, 2024

The ads.txt file is used by website publishers to declare authorized digital sellers for their ad inventory. This file is part of the IAB's (Interactive Advertising Bureau) initiative to increase transparency in programmatic advertising and combat ad fraud. Each line in the ads.txt file represents a different authorized seller or reseller. Here's a breakdown of the components of each line in an ads.txt file:

General Format

<domain>, <publisher ID>, <relationship type>, <certification authority ID>

Components

domain (or Advertising System Domain):

This is the domain name of the advertising system (e.g., the SSP or exchange) that is authorized to sell the publisher's inventory. Example: example.com

publisher ID (or Account ID):

This is the unique identifier associated with the publisher's account on the advertising system. This ID is assigned by the advertising system. Example: 12345 or pub-0000000000000000

Relationship Type:

This indicates the nature of the relationship between the publisher and the advertising system. It can be one of two values: DIRECT: The publisher has a direct business relationship with the advertising system. RESELLER: The advertising system is authorized to resell the publisher's inventory. Example: DIRECT or RESELLER

Certification Authority ID (optional):

This is an optional field that specifies the certification authority ID of the advertising system, issued by the Trustworthy Accountability Group (TAG). It helps to verify the authenticity of the advertising system. Example: 123ABC

Example Line

example.com, 12345, DIRECT, 123ABC

Example Breakdown

example.com: The domain of the advertising system. 12345: The publisher's account ID on the advertising system. DIRECT: The publisher has a direct relationship with the advertising system. 123ABC: The certification authority ID (optional).

Full Example of ads.txt File

google.com, pub-1234567890123456, DIRECT, f08c47fec0942fa0
appnexus.com, 98765, RESELLER, 1a2b3c4d5e
openx.com, 54321, DIRECT

Breakdown of Full Example

google.com, pub-1234567890123456, DIRECT, f08c47fec0942fa0

Google is an authorized seller. The publisher's account ID with Google is pub-1234567890123456. The relationship type is DIRECT. The certification authority ID is f08c47fec0942fa0.

appnexus.com, 98765, RESELLER, 1a2b3c4d5e:

AppNexus is an authorized reseller. The publisher's account ID with AppNexus is 98765. The relationship type is RESELLER. The certification authority ID is 1a2b3c4d5e.

openx.com, 54321, DIRECT:

OpenX is an authorized seller. The publisher's account ID with OpenX is 54321. The relationship type is DIRECT. The certification authority ID is not provided.

Each line in the ads.txt file helps demand-side platforms (DSPs), ad exchanges, and other buyers to verify who is authorized to sell a publisher's ad inventory, ensuring that ad spend is directed to legitimate sellers.