App-Ads.txt FAQ and Guide for PubMatic Publishers


Last year saw massive growth in the adoption of the IAB Tech Lab’s ads.txt standard. Designed to decrease the amount of premium desktop ad inventory that was either spoofed or otherwise heavily arbitraged, ads.txt was successfully embraced by buyers and suppliers, alike.

Today, the industry faces a similar challenge with in-app ad inventory; in-app inventory has an even higher risk for spoofing than desktop inventory due to the lack of visibility into how code is executed within an app. On March 13th, 2019, the IAB Tech Lab released the app-ads.txt standard to battle this rapidly growing threat to the integrity of the ecosystem.

What is app-ads.txt?

Authorized Sellers for Apps (app-ads.txt) is the IAB Tech Lab’s extension to the Authorized Digital Sellers (ads.txt) standard, originally designed for protecting web ad inventory from domain spoofing, arbitrage, and to provide buyers transparency into authorized ad selling. App-ads.txt extends the ads.txt functionality to meet the requirements for applications distributed through mobile app stores, connected television app stores, or other application distribution channels. The specification establishes global standard for validating authorized app inventory sellers.

How is it different from ads.txt?

The main difference between app-ads.txt and ads.txt is how the data crawlers find the file. With ads.txt files, the standard file location is the URL for the website offering up ad inventory for sale (e.g. However, given that apps are downloaded onto devices, there is no obvious location for the app-ads.txt file. The solution adopted by the IAB Tech Lab is for app developers to post their appads.txt file on their company website (e.g. Since app store URLs are an anchor reference for every app, an additional step is required. Crawlers first scrape the app-store page to retrieve the publisher domain URL, and then go to the publisher domain to access the app-ads.txt file.

What do I need to provide to my app developers?

The IAB Tech Lab standard for app-ads.txt entries is the same for ads.txt, consisting of four components:

  1. Exchange URL:
  2. AccountID: This is the PubMatic PubID for your account(s) which will monetize any ad inventory from the app.
  3. Seller Type: Either DIRECT (single hop to DSP: app -> PubMatic -> DSP) or RESELLER (two hops to DSP: app -> publisher -> PubMatic -> DSP)
    • Note: unless the app in question is owned and operated by the PubMatic account holder(e.g. Turner Broadcasting would list DIRECT if selling CNN app inventory), RESELLER should be used.
  4. PubMatic TAG ID: 5d62403b186f2ace
    1. Each part must be included on one line, with each part separated by a comma and a space. All you need to do is substitute the fictional PubID below with your own PubID.
    2. Direct Example:, 111555, DIRECT, 5d62403b186f2ace
    3. Reseller Example:, 111555, RESELLER, 5d62403b186f2ace

What is PubMatic’s policy on app-ads.txt?

PubMatic will allow monetization only of authorized or undeclared inventory.

  • Authorized: If an app has published an app-ads.txt file, you must have the appropriately configured entry included on the file in order to monetize.
  • Undeclared: For apps with no app-ads.txt file posted, monetization will continue.

My App Developer has multiple apps, and wants to post app-ads.txt files for each, but only has a single developer URL. How is this managed?

Developers that want to authorize different sellers for each app must rely on sub-domains. App dedicated sub-domains should be made available in developer URL section of app store page. As an example, Gameloft can set up different sellers for Ice Age Adventures and Brothers in Arms® 3 by updating their app store publisher pages to have subdomain structure. The Ice Age Adventures app can have ‘’ and Brothers in Arms® 3 app can have  ‘’.

Verifier will go to to retrieve authorized seller information for Ice Age Adventures inventory and will go to to do the same for Brothers in Arms® 3 inventory

Many of the apps I monetize don’t see the value in adding app-ads.txt or don’t understand it. PubMatic is in the early stages of planning education and evangelism activities targeting app developers to help them in the following ways:

  • Educate app developers why it’s to their advantage to participate in app-ads.txt
  • Provide resources to help them set up and manage their app-ads.txt file
  • Give app developers tips to avoid the scams and schemes with ads.txt


Special instructions for publishers who are reselling inventory through PubMatic (two hops: app -> publisher -> PubMatic -> DSP)

What are best practices for organizing app-ads.txt entries with multiple authorized resellers (e.g. PubMatic, OpenX, Index)?

As app-ads.txt (and programmatic, in general) is likely new to app developers, you can play a role in helping app developers better organize their ads.txt file. A very simple best practice is to ask your app developer to list all your RESELLER entries (for PubMatic, OpenX, Google, etc.) in a section headed with a hashtag and your company name. This will allow anyone looking at the file to quickly and intuitively determine that you have a direct relationship with the app developer, and the entries included in your section are authorized resellers of the app inventory.

Here’s an example:
## SOVRN ##, 111555, RESELLER, 5d62403b186f2ace, 111556, RESELLER, 5d62403b186f2ace
OpenX, 12345, RESELLER, a1b2c3d4e5f6, 67890, RESELLER, g7h8i9j00j9i8h

Alternatively, you can add a notation after the PubMatic reseller entry to denote the same
relationship:, 111555, RESELLER, 5d62403b186f2ace #Sovrn, 111556, RESELLER, 5d62403b186f2ace #Sovrn
OpenX, 12345, RESELLER, a1b2c3d4e5f6 #Sovrn, 67890, RESELLER, g7h8i9j00j9i8h #Sovrn

Still have questions? Please reach out to your Customer Success Manager.

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