Who owns a website, and how can an ad buyer find out?
Part of Lookalike websites
The short answer
An ad buyer finds who owns a website by stacking evidence: the site's about and legal pages, the OWNERDOMAIN line in its ads.txt file, the company named for its seller ID in exchange sellers.json files, and a state or Canadian business registry record. Where the sources agree, ownership is confirmed; where they cannot be found, record a gap.
Key takeaways
- Ownership is a stack of public records, not one lookup: the site's own pages, ads.txt, sellers.json and a business registry each answer a different part of the question.
- The ads.txt OWNERDOMAIN variable names the business domain of the entity that owns the site, and the specification says it should match the sellers.json domain for that publisher.
- A sellers.json entry names the legal entity that is paid for the inventory, which can be a monetization partner rather than the owner.
- Registries confirm that a named company exists and its status; they do not prove that the company runs a particular website.
How can a buyer find out who owns a website?
Domain registration lookups used to be the first stop, and they now return little. ICANN's Registration Data Policy (opens in a new tab), effective 21 August 2025, requires registries and registrars to redact personal data such as the registrant's name, street address and phone number from public registration output when applicable law requires it, and lets them redact in some other cases. A redacted record says nothing about the publisher either way, so the useful evidence sits elsewhere.
That evidence comes from records the publisher and its sales partners publish on purpose. Google's news transparency guidance (opens in a new tab) asks news sources to show "Information about the company or network behind the content" and "Contact information". The advertising supply chain adds two machine readable files.
Six steps to find who owns a website
- Read the site's own pages. Open the about, masthead, contact, terms and privacy pages, and the footer. Note any company, address, parent group or editor named.
- Open ads.txt at the root domain. Look for an OWNERDOMAIN line and a MANAGERDOMAIN line, and note the CONTACT line if one is present.
- Match the seller IDs. Take the account IDs marked DIRECT and look them up in each exchange's sellers.json file. Record the name and domain given for each.
- Check the structured data. View the page source for schema.org publisher markup, including an ownershipFundingInfo property where the site provides one.
- Look up the company. Search the named company in the registry for the state or province it claims, and note its status and registered address.
- Write the verdict. Record the owner, the sources that agree, any source that disagrees and the date checked.
What does ads.txt reveal about who owns a site?
Version 1.1 of the ads.txt specification (opens in a new tab) added two variables that speak directly to ownership. They are optional, so a file without them is not a warning sign on its own. Where they appear, they are the publisher's own statement of who owns the site and who sells it. The OWNERDOMAIN guide covers the syntax; this page uses the fields as evidence.
Definition
- OWNERDOMAIN
- An ads.txt variable that "Specifies the business domain of the business entity that owns the domain/site/app", in the specification's words. Its value should be a registrable domain, not a full hostname or URL, and the same value as the sellers.json domain for that publisher.
| Element | What the specification says | What it supports | What it does not prove |
|---|---|---|---|
| OWNERDOMAIN | The business domain of the entity that owns the site; if more than one instance is included, only the first should be used | A named parent company, such as a media group's corporate domain | That the parent company is registered or in good standing |
| MANAGERDOMAIN | The business domain of a primary or exclusive monetization partner, used only when the owner does not manage monetization | Separating the company that sells the space from the company that owns it | Who owns the site; a manager can serve several unrelated owners |
| CONTACT | Optional, human readable contact information for the owner of the file | A route to ask the publisher directly | A legal identity; it may be a form or a generic inbox |
| DIRECT account lines | The publisher directly controls the account | Seller IDs to look up in each exchange's sellers.json | Ownership by themselves, until the seller name is read |
How does sellers.json confirm the business behind a site?
Each exchange publishes a sellers.json file (opens in a new tab) listing the accounts it pays. For each seller ID, the name field is "The name of the company (the legal entity) that is paid for inventory that is transacted under the given seller_id", and the domain field is that company's business domain. A DIRECT line in ads.txt that resolves to a PUBLISHER entry with a legal name gives the buyer the paid entity in the exchange's own record.
Two limits apply. The paid entity can be a holding company or a sales partner rather than the brand on the masthead, so the name needs to be matched against the site's own pages. And a seller can be marked confidential: the specification lets the name be omitted only when is_confidential is set to 1. A confidential entry is a gap in the public record, not proof of anything, and the sellers.json explainer covers how to read the other fields.
How do business registries help in the US and Canada?
A registry turns a name on a website into a legal entity with a status, a registered address and, in some jurisdictions, named officers. In the United States, companies register with a state, and the SBA's state registration lookup (opens in a new tab) links to the registration office for each state and territory. In Canada, the federal directories of Canadian companies (opens in a new tab) page links a search across Canada's business registries "by name, business number or registry ID" and a separate federal corporation search.
| Lookup | Where it starts | Search by | Limits |
|---|---|---|---|
| US state business records | The state's secretary of state or corporations office, found through the SBA directory | Entity name, entity number and, in some states, officer or agent | One state at a time; a company may be registered in a state other than the one it names |
| Canada's business registries | The federal directories page | Name, business number or registry ID | Coverage follows the provincial and territorial registries it searches |
| Federal corporation search | The federal directories page | Corporate name, corporation number or business number | Federal corporations only; a provincially incorporated publisher will not appear |
| Publisher structured data | The site's page source | schema.org publisher, Organization and ownershipFundingInfo properties | Self declared and optional; useful to compare with the registry, not to replace it |
Alabama shows the detail a state record can give. The Secretary of State's business entity records (opens in a new tab) can be searched by entity name, entity number, officer, agent or incorporator. The same page warns about potentially fraudulent business filings, a reminder that a registry entry shows a filing exists, not that the filer runs the website.
Why does ownership matter for a site list?
A lookalike search returns sites that read alike, and sites sometimes read alike because one company runs them. Knowing the owner changes three decisions: how much of the plan goes to one business, whether a rule the client applies to one site should apply to its siblings, and who to call when something goes wrong. The lookalike websites hub covers the search itself.
What a confirmed owner lets a planner decide
- The share of the plan going to one company is visible, so a list of twenty sites from four owners is not presented as twenty independent choices.
- A client exclusion of one publisher can be applied to sites the same company runs, if the client wants that.
- Questions about corrections, sponsored labels or ad layout reach a named business.
- Ownership claims on the site match the paid entity in the exchanges' records, or the mismatch is written down.
- The owner and the date checked stay with the list for the next review.
Ownership also connects to concentration, which the publisher concentration guide explains by owner share. Shared ad and analytics codes are a separate signal, covered in the MFA site networks guide and the website similarity guide.
What if a website's owner cannot be found?
Legitimate publishers can leave thin records: a solo writer with a privacy protected domain, a site sold through one partner whose sellers.json entry is confidential, or a small outlet that never added OWNERDOMAIN. None of these is evidence of a problem. Grade the evidence, hold the site at the level it supports, and say so in the plan.
An unknown owner is a reason to ask, through the CONTACT line in ads.txt or the site's contact page, and to hold the site until the question is answered. The unverifiable sites guide shows how to present held sites to a client without counting them as failures.
How does PlacementGraph show who sells each site and which sites share an owner?
What does an ownership check look like on a real lookalike list?
Fictional example
A fictional leather goods maker in Alabama
An unnamed Birmingham maker of leather wallets and belts asks its agency for lookalikes of a Southern men's style blog, for a holiday gift campaign aimed at Birmingham, Huntsville and Mobile. The search returns style blogs, gift guide sites and regional lifestyle magazines.
Two style blogs carry the same OWNERDOMAIN, a small media company's corporate domain, and their DIRECT seller IDs resolve to the same legal name on two exchanges. The planner grades the owner as confirmed and shows the pair as one owner group, so the client sees two sites from one company rather than two independent choices.
A regional magazine names an Alabama limited liability company in its footer. The Secretary of State's records show the company as active, and its sellers.json name matches, so the owner is confirmed. A gift guide site has no about page, a redacted domain record and a confidential sellers.json entry. The planner grades it unknown, writes to the CONTACT address in its ads.txt and holds it. The approved list records owner, sources and date for each site.
Frequently asked questions
Does a privacy protected domain record mean a site is hiding something?
ICANN's Registration Data Policy, in effect since 21 August 2025, requires personal data to be redacted from public registration output where applicable law requires it, so a redacted record says nothing about the publisher. Judge ownership from the site's pages, ads.txt, sellers.json and a business registry instead.
Does a registered company prove a website is a real publisher?
A registry entry shows that a business filed with a state or with Canada and records its status and address. It does not show that the business runs the site, writes its articles or has readers. Treat it as one piece of ownership evidence beside the site's own pages and the exchanges' seller records.
Does the CONTACT line in ads.txt identify the owner?
Not on its own. The ads.txt 1.1 specification describes CONTACT as optional, human readable contact information for the owner of the file, and it may be an email address, phone number or contact form. It gives a buyer a way to ask the question, while OWNERDOMAIN and sellers.json give the answer.
What should a buyer ask a publisher about ownership?
Ask for the legal name of the owning company, any parent, the business domain it would list as OWNERDOMAIN, which partner manages its ad sales, and whether it runs other sites. Compare the answers with ads.txt and sellers.json before marking the owner confirmed.
Sources
- ads.txt Specification Version 1.1 (opens in a new tab)IAB Tech Lab
- Sellers.json specification (opens in a new tab)IAB Tech Lab
- Registration Data Policy (opens in a new tab)ICANN
- Google News policies: transparency (opens in a new tab)Google Publisher Center Help
- State registration lookup (opens in a new tab)U.S. Small Business Administration
- Directories of Canadian companies (opens in a new tab)Government of Canada
- Business entity records (opens in a new tab)Alabama Secretary of State
- ownershipFundingInfo (opens in a new tab)Schema.org
Researched and written by PlacementGraph Research. Read how we research, source and update these pages. Corrections: diana@placementgraph.com.