An abbreviation for “Authorized Digital Sellers”, ads.txt files are the online advertising industry’s latest tool in the battle against ad fraud. The purpose of ads.txt files is to give advertisers and advertising networks the ability to verify who is allowed to sell advertising on your website. This process is automated using “crawlers”, which are automated computer programs which index ads.txt files, much like a search engine. This information is then used by advertisers and ad networks, with this process normally being automated as part of the ad buying process.

Just like a robots.txt file on your website, the ads.txt file is created at the root of your domain (e.g. https://yourdomain.com/ads.txt). The file is a standard plain-text file which simply contains a list of ad network domain names, each with an associated ID.

The format logically consists of:

1. A non-empty set of records, separated by line breaks. The records consist of a set of lines of the form: <FIELD #1>, <FIELD #2>, <FIELD #3>, <FIELD #4> or =.
2. Records contain comma-separated fields, 3 fields are required, 1 field is optional.
3. An ads.txt file can include comments, by simply beginning a line with a hashtag the rest of the line will not be indexed by crawlers.
4. An ads.txt file can also contain contact information, and if the website uses subdomains then these can be referenced to inform crawlers that additional ads.txt files exist on these subdomains.
5. From version 1.0.3 the ads.txt file can contain inventorypartnerdomain - a pointer to the domain of an entity that is explicitly authorized to monetize ads within application's content. The partners corresponding appads.txt or ads.txt file will be hosted at this domain.

Example ads.txt file:

google.com, pub-770011223344550606, DIRECT, f08c47fec0942fa0
admixer.net, E1DF631C-1269-4EF3-A0FF-452A8B59DCB2, RESELLER
# An example comment
adtech.com, 11456, DIRECT #next comment
contact=support@windows10gadgets.pro
contact=https://windows10gadgets.pro/contact.html
subdomain=blog.domain.com
subdomain=news.domain.com
inventorypartnerdomain=programmerA.com

The ads.txt specification specifies that whilst the records in an ads.txt file must follow the defined structure, the basic formatting of the file is not strict. For example, the presence or lack of spaces around the comma delimiters, and the presence of white-space between records will not affect how the ads.txt file is crawled. The text file can be created just like any other text file, using any text editor, on any computer operating system.

Errors

Errors are serious issues which may invalidate your ads.txt file or cause lost revenue, they must be resolved immediately.

1. Incorrectly formatted data records and variables.
2. Invalid or incorrect exchange domains, publisher IDs, relationship values, and certification authority IDs.
3. Invalid lines which are not valid ads.txt records.

Warnings

Warnings highlight points of concern but which should not affect the processing of your ads.txt file, but which should be resolved as soon as possible.

1. Potentially invalid exchange domains.
2. Invalid variable names (not CONTACT, SUBDOMAIN or INVENTORYPARTNERDOMAIN).
3. Invalid contact, subdomain and inventorypartnerdomain variable values.
4. Duplicate ads.txt records (comments will be ignored, including inline comments included after data records).

Notices

Notices provide information on how to improve the formatting of your ads.txt file.

1. Inconsistent case and unnecessary whitespace.