Short answerads.txt (Authorized Digital Sellers) is a plain text file at the root of your domain — yourdomain.com/ads.txt — that lists the ad systems allowed to sell your inventory, with your account ID and relationship for each. Buyers check it before bidding, so without it many of them skip your impressions.
ads.txt is one of the simplest things a publisher can do to protect revenue. It takes minutes to set up and tells every buyer which sellers are real. This guide explains the format, where the lines come from and how to avoid the usual mistakes.
What is ads.txt?
ads.txt is an IAB Tech Lab standard introduced in 2017 to fight domain spoofing — selling fake inventory under the name of a real site. The publisher publishes a list of authorized sellers; a buyer that receives a bid request for your domain checks whether the seller is on that list.
It works together with sellers.json and the SupplyChain object: ads.txt says who may sell your inventory, sellers.json says whom each ad system pays, and schain shows the path of each impression.
What does an ads.txt line look like?
Each line has three or four fields separated by commas:
The domain of the SSP or exchange that sells your inventory
Publisher account ID
Your account ID in that system (matches seller_id in its sellers.json)
Relationship
DIRECT if you control the account, RESELLER if a partner resells your inventory
Certification authority ID
Optional, for example a TAG-ID
The lines above are examples. Always copy the exact lines your partners give you.
Variables in ads.txt 1.1
The current version of the specification also supports variables, for example:
CONTACT= — who to contact about the file;
OWNERDOMAIN= — the business domain of the owner of the site;
MANAGERDOMAIN= — the domain of a company that manages your inventory, if any;
SUBDOMAIN= — subdomains that have their own ads.txt.
How do you create and publish ads.txt?
Collect the lines from every ad partner. They are usually in your dashboard or provided by your manager.
Create a plain text file named ads.txt, one entry per line. Comments start with #.
Upload it to the root of your domain, so it opens at https://yourdomain.com/ads.txt.
Check that it is served as plain text with an HTTP 200 response, without a redirect to another domain or a login page.
Update it whenever you add or remove a partner.
On most CMS platforms you can upload the file through hosting, an FTP client or a plugin.
Common mistakes
Mistake
What happens
Fix
File not at the root
Buyers cannot find it
Publish at /ads.txt on the main domain
Typos in the account ID
The seller looks unauthorized
Copy lines exactly from the partner
Wrong relationship
Buyers distrust the path
DIRECT only for accounts you control
Old partners left in the file
Confusing, sometimes risky
Remove lines for partners you no longer use
File returns an HTML page
Invalid file
Make sure the server returns plain text
What is app-ads.txt?
app-ads.txt is the same idea for mobile and CTV apps. The file is published on the developer's website listed in the app store, and buyers use it to check sellers of in-app inventory.
How do you check your file?
Open https://yourdomain.com/ads.txt in a browser and read it.
Ask each partner whether they see their lines correctly.
Many ad platforms show an ads.txt status in their dashboards; fix any warnings they report.
ads.txt and Wizads
When you join the Wizads SSP, your manager provides the exact ads.txt lines for your account. Add them to the file at the root of your site; this tells buyers that Wizads is authorized to sell your inventory and helps your impressions get more bids. For the bigger picture, read our website monetization guide.
Frequently asked questions
Is ads.txt mandatory?
No law requires it, but many buyers do not bid on inventory from domains without ads.txt or on sellers missing from it. In practice it is required for good revenue.
Does ads.txt affect SEO?
No. It is read by advertising systems, not used for ranking.
What if I have several domains?
Each domain needs its own ads.txt. Subdomains can be covered with the SUBDOMAIN= variable on the main domain.
Wizads is an advertising network with its own DSP, SSP and ad server. Our team writes about programmatic advertising, website monetization and buying traffic.
