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Ads.txt FAQ for Sellers

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What is ads.txt?

The goal of Ads.txt is to give publishers a way to list ALL their approved SSP, ad network, and exchange partners (both direct and resellers). Theoretically, the publisher’s inventory should not be found via other partners.

Technically, Ads.txt is a file the publisher places on their domain ( Within the file each approved partner is listed with their tech platform (AppNexus, Google, Rubicon, etc.), account detail, and the relationship. DSPs & SSPs will regularly crawl these files to discover the approved inventory sources.

How is AppNexus as a DSP going to use ads.txt files?

AppNexus is using Ads.txt information as a way to strengthen our existing inventory quality programs.

How should publishers or networks incorporate their AppNexus accounts into their ads.txt file?

For more information on how publishers and networks should use ads.txt, see AppNexus Support for Ads.txt.

Is AppNexus recommending that all publishers and networks implement ads.txt?

Ads.txt is new and the IAB spec is evolving, but AppNexus supports these efforts. Early implementation on the client side may help clients get up to speed as ads.txt becomes more ubiquitous. 

Where can I find an example ads.txt file?

There are some samples of what ads.txt files should look like in AppNexus Support for Ads.txt.

What percentage of AppNexus publisher clients are ads.txt compliant? 

77% of our top 1000 publishers are compliant and have ads.txt files on their domains.

How often does AppNexus' crawler update?


How is ads.txt currently being used by AppNexus buyer clients? 

Buyers (both Console clients and external bidder clients) benefit from AppNexus' daily ads.txt file crawling and enforcement because, by default, they only buy from compliant sellers if a domain has an ads.txt file associated to it. Buyers do not have the option to target any differently because AppNexus simply suspends supply paths in violation of information found in sellers' ads.txt files.

What percentage of buyers are actively crawling publishers' files currently? At what cadence? Is this number expected to rise in the near future?

We have no way to know which bidders are crawling and which are not. Some buyers have publicly said that they both crawl for ads.txt files and enforce inventory standards on the basis of these results. AppNexus performs scanning and enforcement on a daily basis. 

Can publishers be blocked by buyers because they do not support ads.txt or their file is incorrect?

If a publisher has a file in error (meaning they don't include all their sellers that are authorized), then that has the potential impact them. If a file is found that appears unintentionally broken or corrupted in some way, AppNexus will check with publishers rather than immediately disable buying from parties whose information is not found in the file. 

Why isn't AppNexus enforcing ads.txt compliance for external bidder demand?

We are not enforcing ads.txt compliance for external bidders because we anticipate that many of our external bidder partners will be rolling out ads.txt detection and enforcement mechanisms within their own systems, and wanted to avoid duplication of logic.

For bidders who are buying external SSP demand via AppNexus and are building out their own ads.txt compliance mechanisms, we recommend they implement enforcement mechanisms in a similar fashion to AppNexus - if the SSP is listed in the file, then treat them as an authorized relationship via AppNexus.

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