Glossary/Programmatic/ads.txt
What is ads.txt and why do publishers need it?
What ads.txt is, how buyers use it, and how publishers keep the file clean.
Written by Samhub with the help of AI·Updated 13 Oct 2026·3 min readads.txt (Authorized Digital Sellers) is a public text file on a publisher’s domain that lists the companies allowed to sell its ad inventory. It was introduced by IAB Tech Lab in 2017.
How it works
Publisher lists sellers
At yourdomain.com/ads.txt.
Buyers check the file
Before bidding on an impression.
Unlisted sellers are skipped
Which stops spoofed inventory.
What a line looks like
| Field | Example |
|---|---|
| Seller domain | ssp-example.com |
| Account ID | Your account at that seller |
| Relationship | DIRECT or RESELLER |
| Certification ID | Optional |
16 pages for publishers, with a checklist for data, programmatic and direct sales.
Keep it clean
Remove partners you no longer use and avoid long lists of resellers. A short, accurate file helps buyers find the direct path to your inventory.
CPM uplift at Stampen Media after activating first-party audiences with Samhub.
Frequently asked questions
Not by law, but many buyers will not buy without it.
The same idea for mobile apps.
Whenever you add or remove a partner.
ads.txt lists who may sell; sellers.json shows who the sellers are.
Related terms
Shows who the sellers in the chain are.
Buyers choosing the shortest, cleanest route to inventory.
The software publishers use to sell impressions.
Impressions and clicks not made by real, interested people.
Samhub audiences let you set higher floors and win more data deals, in every channel you sell.
- A walkthrough with your own data
- Built for publishers and media houses
- 30 minutes, no commitment
Turn your audience data into more revenue
Get the Media Monetization Playbook: how media houses turn first-party data into higher CPMs, data deals and direct sales. With checklists for every step.
