Authorised Digital Sellers

Ads.txt - Desktop and Mobile Web Inventory


To combat fraud and maximise transparency in the advertising ecosystem, the Authorised Digital Sellers (ads.txt) aims to stop profits spoofed inventory. This is a type of fraud where fraudsters sell fake inventory and collect the profits. Read more about the issues of transparency and counterfeit inventory here.

How it works

Every website that has advertising contains an ads.txt file containing a list of the authorised sellers. Demand partners (buyers, DSPs, etc.) can check these files and confirm if the ad tech platform domain and account number match the data in the bid requests they receive; if there is no match, the request might be considered fraud and rejected.

From IAB, About Ads.txt

How to implement ads.txt

If you own the website or are the advertising operator on behalf of the owner:

  1. Login to 360 Polaris and hover over the account name to see the Publisher ID
  2. Create a text file and paste:, [publisher ID], DIRECT
  3. Upload the file to every website at the root domain, for example:


  1. Login to 360 Polaris and hover over the account name
  2. Send the following information to your publishers:, (Your Publisher ID), RESELLER

Additional options in ads.txt

It's possible to add extra information into the file, including:

  • Comments
    Any additional information, lines which are comments must start with a hashtag '#'.
  • Contact
    Shows contact info for content providers support team. Can be an email address, webpage, etc. There can be multiple lines, each one should start 'contact='.
  • Subdomain
    Direct the crawler to an ads.txt file on the subdomain. Used if the sellers differ from the root domain. The ads.txt file in the subdomain is not associated with the root domain, i.e. it's considered as a different site. If there are multiple subdomains, mention them in separate lines (like in the Ads.txt example below).
  • Certification Authority ID
    An optional additional field in each ad tech provider listing is an ID from an independent certification authority, which would effectively verify if this ad tech provider is genuine and trusted. Improve Digital has trusted relationships with demand partners and does not make use of this field as yet.

Example of ads.txt

In the following example:

  • the publisher sells their inventory through their own Improve Digital account,
  • also via a third party who happen to use a different Improve Digital account,
  • has subdomains with which are sold through different sellers to the root domain,
  • and wants to include contact information

therefore the ads.txt file would be:

  #ads.txt for, 2001, DIRECT, 1988, RESELLER

Lines starting with # symbol are considered comments and are ignored by ads.txt crawlers.

Ads.txt FAQs

  • Can there be an ads.txt on just one of the main sites I own?
    This is possible using a redirect from the site to the ads.txt on another domain. Only one redirect is currently allowed. More information is available in the IAB spec linked below. Ideally each domain should have this file, even if all domains are owned and operated by the same content owner, and even if the file is identical in content. 
  • Does the file have a cache? If yes, how long is it?
    The file is scanned by DSP crawlers every so often, possibly several times a week, but this depends entirely on the DSP's technology and settings. It is not expected that the ads.txt file will be regularly updated.
  • Does the file have to put onto a website or is it also possible to do it via a 301/302 to a CDN?
    Yes this is possible, see the IAB spec linked below.
  • I have tags from other platforms such as Criteo, OpenX etc. in 360 Polaris. What do I put in my ads.txt file?
    If you are using 360 Polaris as an ad server and have third-party tags booked, your ads.txt file should list your account on the third-party platforms. Although the tag is competes in the 360 Polaris auction, the ad request runs via the third-party platform, not via Improve Digital demand partners.
  • What happens if I don't have an ads.txt file?
    Buying partners will assume that there are no authorised programmatic sellers.

Useful Links

This article is based on Ads.txt Spec Version 1.0.1


App-ads.txt - Apps


As part of the industries commitment to combatting ad fraud, the IAB released the app-ads.txt specification, an update to the ads.txt to specifically support mobile and OTT apps. Industry adoption of the standard is on the rise, with demand partners shifting spend towards validated sources of inventory.

The format of the file is the same as ads.txt, with the list of exchanges authorised to sell the inventory, the account IDs and account type - direct or reseller. The app-ads.txt file should be hosted on the developer's website which is provided in the app's page on app stores.

How to implement app-ads.txt

The format of the file is identical to ads.txt - see above example. The implementation of these steps must be taken by app developers/media owners based on the information that sellers provide:

  1. Create a .txt file named 'app-ads.txt'
  2. List all of the ad networks authorised to sell or resell the inventory
  3. Add an entry for with the seller account ID from Improve Digital
  4. Provide the developer website URL in the app store of the app
  5. Post the file to the root directory of the developers website; for example,
  6. Update the file every time there is a new seller or reseller added or removed from buying publisher’s inventory

Benefits of app-ads.txt

Without this file, demand partners will assume that everyone is authorized to resell publishers’ inventory. By not implementing the file, media owners could become more susceptible to domain spoofing and unauthorised transactions, with buyers also unable to know if the inventory is genuine or spoofed.

For sellers of app inventory, implementing app-ads.txt is essential to securing advertiser spend from Q3 of 2019 onwards.

Further information

Read the IAB app-ads.txt specification and FAQ documents for more information.