How to verify an ad network’s publisher claims before you sign

Every ad network shows prospective publishers a list of impressive sites it works with. Some of those relationships are current and central; some ended two years ago; some were never what the slide implied. From the outside these look identical.

They are not identical in the public record, and the check takes about twenty minutes.

The principle

Both sides of every advertising relationship are obliged to publish. The network declares the sellers it represents in its sellers.json; the publisher declares who may sell its inventory in its ads.txt. Either document alone is one party’s assertion. Together they are an agreement, because two independent parties had to take an action for both to say the same thing.

So the question to ask about any claimed relationship is not “does the network say so” but “does the publisher say so too”. If you only remember one thing from this page, that is it. The mechanics of both files are covered in ads.txt and sellers.json explained.

The check, step by step

• Get the network’s roster. Open thenetwork.com/sellers.json. Search it for the marquee domains you were shown. If a site the network told you about is not in its own seller file, ask why before anything else.
• Note the seller id. Each entry carries the account id that publisher holds with the network. This is what you will match on.
• Check the publisher’s side. Open thatpublisher.com/ads.txt and look for that account id. Present means both parties agree. Absent means only the network is claiming it.
• Look at the page. Load the publisher’s homepage and check what ad code it actually loads. This is present-tense evidence where the files are paperwork.
• Repeat across five or six names, not just the most famous one. A single confirmed relationship tells you a network has one real publisher. The pattern across several tells you whether its roster is broadly real.

The confirmation rate for every network we track

A low rate is not automatically an accusation

This matters, and articles that publish tables like the one above rarely say it. There are legitimate reasons a network’s published roster goes unconfirmed:

• Reselling. A network that sells through upstream partners may never appear under its own name in a publisher’s file. The relationship is entirely real and structurally invisible from the publisher side.
• Shared seats. Agencies and networks sometimes place several publishers under one account, so the id in the publisher’s file does not match the one published for that specific domain.
• Unreadable publisher files. Some sites serve no ads.txt, or serve it in a way crawlers cannot read. Absence of evidence, not evidence of absence.
• Stale entries. The publisher left and the network has not pruned the file. This one is a problem, and it is the most common.

Which is why the table is a prompt for a question rather than a verdict. A network at the low end is not necessarily misrepresenting anything — but it is a network whose published roster you should not take at face value, and it is entirely fair to ask it which of the four explanations applies.

What to ask a network directly

Three questions, all reasonable, and the quality of the answers is informative regardless of the numbers:

• “Are the publishers on your deck currently live?” Ask for a date. Vagueness here is the clearest signal available.
• “Will my site appear in your sellers.json under my own domain?” A yes is a commitment to a public, checkable record of the relationship. A no may be legitimate — confidential sellers are permitted — but you should understand why.
• “How quickly do you remove publishers who leave?” A network that prunes promptly is one whose claims about anything else are more likely to be accurate.

Why this check is worth doing at all

Because the roster is a proxy for the two things you actually care about and cannot see. A network with real, current, comparable publishers has demand relationships that work for inventory like yours. A network whose published roster is substantially aspirational may still be perfectly good — but you have just learned that its public statements need verifying, which is a useful thing to know before signing a contract.

Every network we track has a page here with its full indexed publisher list and the evidence behind each match — start from all networks. The rules we apply are on the coverage & method page.

“Confirmed” means the publisher’s own ads.txt or homepage evidences the network. Unconfirmed relationships may still be real; see the four explanations above. Every figure on this page is read from our own index when the page is built, and refreshes on a weekly cycle — so the numbers move as the data does. Method and evidence rules: coverage & method.