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App-ads.txt extends ads.txt functionality to include inventory from mobile apps and over-the-top (OTT) video. The new app-ads.txt specification relies on the publisher URL, available on app store HTML pages, as the centrally located, crawler-friendly, trusted source.  

Ads.txt is an open standard and technical specification defining how a publisher can publicly declare their list of “Authorized Digital Sellers,” in an “ads.txt” on their site. It is a simple, flexible, and secure way for content owners and distributors to declare who is authorized to sell their inventory, improving transparency for programmatic buyers. Learn more in the Ads.txt Implementation Guide.

How app-ads.txt Works

The specification identifies four entities that play a vital role in enabling authorized digital seller validation on in-app inventory:

  • App stores
  • App publishers
  • Sell-side platforms
  • Authorized seller verifiers

App stores enable mobile authorized seller specifications. They connect the app with its publisher’s URL that hosts seller information. Specification requires the app stores to publish the app publisher’s URL, bundle_id, and store_id as HTML <meta> tags within the <head> tag at the beginning of the HTML doc.

App publishers complete the following steps to enable seller authorization on their app inventory:

  1. Register the URL that hosts app-ads.txt file on the app store
  2. Publish an app-ads.txt file with authorized seller information.

The file format for mobile authorized seller information will be identical to that of web ads.txt. Each record will have an ad tech domain, publisher account ID, relationship\account type and optional TAG ID.

Please note that app inventory seller information must be published in a separate file entitled “app-ads.txt.” Therefore, the web seller information will be available in “ads.txt” but independent of app seller information.

Sell-side platforms are required to include a store URL parameter on all bid requests. Only requests with valid store URL parameters are eligible for authorization.

Authorized seller verifiers must follow the below steps to verify authorization:

  • Identify the app store URL in the bid request
    • Crawl the app store URL page for the publisher’s URL, bundle_id and store_id
  • Translate the publisher URL to an app-ads.txt path
  • Crawl and interpret the app-ads.txt file for enforcement

Mobile app-ads.txt specification ignores sub-domain directives, unlike web ads.txt file. Under web ads.txt specification, verifiers are expected to crawl the root domain and parse sub-domain directives to track sub-domains to specific authorized sellers.

In-app environment verifiers must start at second level domains and then fall back to root domains only when there is a missing file. This special provision is made to handle app-specific authorized seller information.

How to Implement app-ads.txt

App developers should follow these steps to adopt app-ads.txt for their apps.

  1. Provide the developer website URL in the app store listings.

    This is required for the app's ad inventory to participate in the authorized seller scheme.

  2. Create the app-ads.txt file. (The filename must be app-ads.txt.)
  3. Add an entry in the file with the standard file format:

Field No.FieldDescriptionExampleStatus
1Domain name of the advertising systemThe domain of the systempubmatic.comMandatory
2Publisher Account ID2546325463Mandatory
3Type of Account RelationshipCan be either DIRECT or RESELLER relationshipDIRECTMandatory
4Certification Authority IDID that identifies the advertising system within a certification authority (mapped to entity in field #1)5d62403b186f2aceOptional

Example: ', 25463, DIRECT, 5d62403b186f2ace'

4. Post the app-ads.txt file to your domain's root directoryon the app store publisher URL (on the app store page).

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