Declare authorized sellers with ads.txt

Authorized Digital Sellers, or ads.txt, is an IAB initiative to improve transparency in programmatic advertising. You can create your own ads.txt files to identify who is authorized to sell your inventory. The files are publicly available and crawlable by exchanges, Supply-Side Platforms (SSP), and other buyers and third-party vendors.

Use of ads.txt is not mandatory, but is highly recommended. It can help protect your brand from counterfeit inventory that’s intentionally mislabelled as originating from a specific domain, app, or video. Declaring authorized sellers can help you receive advertiser spend that might have otherwise gone toward counterfeit inventory.

These instructions describe how to create an ads.txt file for Google publishers. Non-Google publishers should contact their SSP or exchanges.

Learn how to automatically generate ads.txt content in Ad Manager.

Watch related Publisher University training

Create an ads.txt file

Create a text file named ads.txt and include separate lines for each exchange or SSP that is authorized to sell your inventory. Each of these lines should contain three pieces of data (plus a fourth optional field), in the format:

<Field #1>, <Field #2>, <Field #3>, <Field #4>

  • <Field #1>: The canonical domain name of the system where bidders connect. This may be the operational domain of the system, if it’s different than the parent corporate domain, to facilitate WHOIS and reverse IP lookups to establish clear ownership. The SSP or exchange may publish the domain name to use.

    For Google seller accounts, the domain name is always google.com.

  • <Field #2>: The publisher identifier associated with the seller or reseller account for the system in field #1. This must contain the same value as that specified in an SSP or exchange transaction (such as OpenRTB bid requests). Typically, in OpenRTB, this is the publisher.id field. For OpenDirect, it is typically the publisher’s organization ID. 

    For Google seller accounts, use the publisher ID displayed in each account (for example, pub-0000000000000000). To find this ID:

    Only include the pub- prefix and the 16-digit numeric code in your declaration. Delete the product-specific prefix (for example, ca- or ca-video-). If you monetize through multiple Ad Manager and/or AdSense accounts, you must include a separate row for each account, with its corresponding pub- code.
    Domains hosting an ads.txt file where the seller’s publisher ID isn’t listed are no longer monetized through Ad Manager, and Google no longer buys ads on such sites. Updating your ads.txt files to include publisher IDs for each site you want to monetize is recommended (learn how to update ads.txt in Ad Manager). If you use Scaled Partner Management, we recommend working with your child partners to include your publisher ID in their ads.txt files.
  • <Field #3>: The type of account or relationship. This field should be treated as case-insensitive when interpreting the data.
    • A value of 'DIRECT' indicates that the publisher (content owner) directly controls the account indicated in field #2 and has a direct business contract between the publisher and the advertising system.

      Google publishers who directly control the account indicated in field #2 should specify 'DIRECT'.

    • A value of 'RESELLER' indicates that the publisher has authorized another entity to control the account indicated in field #2 and resell their ad space via the system in field #1.

      Google publishers who don't directly control the account indicated in field #2 should specify 'RESELLER'. For example, an Ad Manager account using Scaled Partner Management should specify 'RESELLER' for inventory the account doesn't directly manage.

  • <Field #4>: (Optional): A unique identifier for the advertising system within a certification authority, which maps to the entity listed in field #1. One certification authority is the Trustworthy Accountability Group (TAG), and the TAG ID would be included here.

    For Google seller accounts, the TAG ID is f08c47fec0942fa0.

Host the ads.txt file

Host the ads.txt file at the root level of your domain. Root levels are one level down from what’s listed in the public suffix list. For example, "google.co.uk" is a root domain of "co.uk" but "maps.google.co.uk" is not. See the IAB ads.txt specification.

Examples of ads.txt files

Publishers working with Google products should always use google.com as the domain name, with their publisher ID. For example:

google.com, pub-0000000000000000, DIRECT, f08c47fec0942fa0
google.com, pub-0000000000000000, RESELLER, f08c47fec0942fa0

Publishers working with other non-Google products should list their SSP or exchange domain names, with their seller account IDs. For example:

greenadexchange.com, 12345, DIRECT, AEC242
blueadexchange.com, 4536, DIRECT
silverssp.com, 9675, RESELLER

Frequently asked questions

How does Google enforce ads.txt files?

Google uses the content of any ads.txt files hosted on a root domain to determine which seller accounts are allowed to serve ads on that domain. No additional enforcement exists for root domains without an ads.txt file.

Google runs an auction and returns a winning ad for requests on sites where an ads.txt file exists with a correctly listed publisher identifier. If the identifier in the file is incorrect, an auction is not run for that request.

New and updated ads.txt files are detected automatically, but changes may take up to 24 hours.

What if the ads.txt file is hosted on a subdomain?

Google crawls and enforces ads.txt files placed on subdomains, where one exists, and is referenced from the ads.txt file on the root domain. The ads.txt management tool does not yet show a list of crawled subdomains.

Does Google support redirects?

Google supports a single HTTP redirect to a destination outside the original root domain (for example, example1.com/ads.txt re-directs to example2.com/ads.txt). See the IAB update.

Multiple redirects are also supported, as long as each redirect location remains within the original root domain. For example:

  • example.com/ads.txt redirecting to www.example.com/ads.txt
  • example.com/ads.txt redirecting to subdomain.example.com/ads.txt
  • example.com/ads.txt redirecting to example.com/page/ads.txt

How do I set up an ads.txt file for Blogger?

See the Blogger Help Center for instructions.

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