Declare authorized sellers

ads.txt/app-ads.txt and inventory sharing partners (Beta)

Inventorypartnerdomain (IPD) is a relatively new IAB field and some DSPs may not yet validate statuses based on it, even if Ad Manager is sending the value in the bid request. If you implement IPD, in the short term, continue to keep existing direct/reseller declarations within the ads.txt/app-ads.txt

In March 2021, the Interactive Advertising Bureau (IAB) updated the ads.txt/app-ads.txt specification to support a new directive called “inventorypartnerdomain” that maps the inventory sharing relationships that are common to (but not limited to) Connected TV (CTV) and over-the-top (OTT) streaming video services.

Adopting the inventorypartnerdomain specification is optional, but it allows publishers to more easily manage their app-ads.txt/ads.txt files. Previously, publishers engaged in inventory sharing would have to list all the domains related to the inventory sharing partner and the corresponding resellers of that partner that are authorized to sell their content. Managing the app-ads.txt/ads.txt files becomes difficult if updates are needed in the case where there are multiple inventory sharing relationships and/or the inventory sharing partner is engaged in complex reseller arrangements.

By adopting the inventorypartnerdomain specification within the app-ads.txt/ads.txt, publishers can designate the domain of their inventory sharing partner and buyers can also look up the ads.txt of the inventorypartnerdomain to validate authorized resellers (in addition to looking up the ads.txt/app-ads.txt file of the publisher).

Note that using the inventorypartnerdomain declaration means that the publisher accepts all entries in the partner’s ads.txt/app-ads.txt file as authorized to sell their inventory and the publisher assumes the risk of any changes to that file with or without their knowledge.

Get started with inventorypartnerdomain

  1. List inventory sharing partners in your ads.txt/app-ads.txt file by adding the new inventorypartnerdomain entry.
    Let’s assume there’s an inventory sharing relationship between Programmer A (who creates content) and Distributor B (who owns the CTV app that aggregates content). Programmer A has rights to sell ads for their owned content that appears in Distributor B’s app.
    Within their app-ads.txt file, Distributor B specifies the domain of their inventory partner, Programmer A, as follows:

  2. Update the VAST ad tag to append the &ipd parameter. In order for validation based on inventorypartnerdomain to occur, ipd must be specified on the ad request and match the domain of the inventory partner listed in the app-ads.txt/ads.txt file. If ipd is not specified on the ad request, then validation based on inventorypartnerdomain will not occur.
    A user visits content owned by Programmer A within Distributor B’s CTV app.
    To reflect the inventory sharing relationship, the &ipd parameter is specified within the VAST ad request from Distributor B’s app, as follows:


  3. Reach out to your inventory sharing partner to make sure that they have a properly set up the ads.txt file hosted at the domain that you indicated in step 1.

There are many types of inventory sharing relationships. For example, there may be implementations where the opposite occurs (Programmer A specifies Distributor B as the inventorypartnerdomain). For more examples, see the IAB Guidance for Inventory Sharing.

Troubleshooting inventorypartnerdomain implementations

  1. Ensure inventorypartnerdomain is correctly declared in the ads.txt/app-ads.txt file and the VAST ad requests.
    1. Domains should be specified as root domains (for example, instead of
    2. Declaration of inventorypartnerdomain is one line with no spaces.
    3. The pointer to the domain of the inventory partner is correct (where the inventory partner hosts their ads.txt file for the corresponding environment for where you are making the request). For example, Programmer A might be using for their CTV Google TV inventory and for their CTV Apple TV inventory.
    4. Only one inventorypartnerdomain can be specified per line in the ads.txt/app-ads.txt file (if there are multiple IPDs, each one should be declared in their own separate line).
    5. The &ipd parameter in the VAST ad tag can only take one domain declaration.
  2. Work with your inventory partner to make sure that their ads.txt file is correctly set up with the correct publisher codes and the file is crawlable.
    1. Declarations of inventorypartnerdomain on a publisher’s ads.txt/app-ads.txt would only point to the inventory sharing partner’s ads.txt file (not the app-ads.txt file).

Frequently asked questions

Do I need to update my ads.txt/app-ads.txt file for each app store/web domain?

You should upload an ads.txt file for every associated web domain and app-ads.txt for every associated mobile app and CTV app across each app store.

If you want to use inventorypartnerdomain, you only need to update the corresponding ad requests and ads.txt/app-ads.txt files for the app stores/domains in which you engage in inventory sharing.

Different environments might have different ads.txt/app-ads.txt files set up if you have seller/reseller relationships that differ by environment.

Does ads.txt/app-ads.txt support both inventorypartnerdomain and reseller declarations for inventory sharing?

Yes. IPD is an optional specification and buyer validation of ads.txt/app-ads.txt will still take into account any seller/reseller IDs that are listed in the ads.txt/app-ads.txt file.


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