You finished the site, applied to an ad network, and nothing serves. Often the block isn’t your content or your traffic – it’s a missing text file at your domain root that the network uses to confirm the ad space is really yours to sell.
https://yoursite.com/ads.txt – that lists which advertising systems are allowed to sell your ad inventory. Each line names an ad system’s domain, your publisher account ID on that system, and whether the relationship is DIRECT or RESELLER. Before a network serves or pays for ads, its crawler fetches that file and checks that your account is listed; if the file is missing, returns a 404, or still names a previous owner, the network treats your inventory as unauthorized and holds back. It is public by design, and it is one of the quickest launch checks to get right.Served at /ads.txt, plain text, returns 200. Not in a subfolder.
system domain, your publisher id, DIRECT or RESELLER.
Crawler reads it, confirms it's your inventory, serves ads.
No file, a 404, or a previous owner's line = the network won't serve or pay. It is public by design.
Table of Contents
What the file actually says
Each line is a short record with three required fields and an optional fourth:
- The ad system’s domain – the canonical domain of the network or exchange, e.g.
google.com. - Your publisher account ID – the identifier that system knows you by. This is not a secret; it is meant to be published, which is the whole point of the file.
- The relationship –
DIRECTif you have a direct account with that system, orRESELLERif a third party sells the inventory on your behalf. - A certification authority ID (optional) – a short code that further ties the record to the system.
A crawler reads those records literally. A typo in the domain, the wrong account ID, or the wrong relationship type is the same as not being listed at all: the record simply doesn’t match, and the matching ad requests go unfilled.
ads.txt is not a setting you toggle; it is a claim you publish. The network believes the file, so the file has to be exactly right.
Why a network insists on it
ads.txt exists to stop domain spoofing – bad actors reselling ad space they don’t own by claiming to represent a real site. By publishing the authorized-seller list at your own root, you let any buyer verify, independently, that a given seller is really allowed to sell your inventory. That protection only works if the file is present and correct, so networks enforce it: no valid record, no served ad. For a brand-new site this is a common invisible blocker – the application is fine, the content is fine, but the empty or absent ads.txt quietly fails the check.
Where it has to live
Two rules trip people up. First, location: the file must be at the domain root (/ads.txt), not in a subfolder and not behind a redirect chain – the crawler looks in exactly one place. Second, status: it must return HTTP 200 as plain text. A page-not-found that serves your themed 404 with a 200 status (a soft 404) can even make an absent file look like a broken one. On a subdomain, the rules get more specific, and a multisite or subdomain setup may need its own file per host. Confirm the raw file loads in a browser at the root before you assume it’s being read.
What our own site did with a missing file
Before applying to an ad network, we requested /ads.txt on our own site, anonymously. We had no file yet, so we expected a 404. We got a 301 to our own article about ads.txt. WordPress, finding no such page, looked for the post with the closest-looking slug and redirected to it. A crawler following that lands on an HTML article where it expects a plain-text list of sellers: a broken file rather than a missing one.
We turned that guessing off (details in our soft 404 write-up), and /ads.txt now answers a clean 404 until there is a real file to serve. Once the file exists in the web root, the web server hands it out before WordPress is even involved, so the redirect can no longer get in the way. The check worth copying: request /ads.txt before you create it. If the answer is anything other than a 404, find out why first.
Getting it right at launch
Treat it as a launch gate, not an afterthought – it belongs in the same pre-flight pass as your go-live audit. The sequence is simple: get your publisher account ID from the network, create the ads.txt file with the exact record it gives you, place it at the domain root, load yoursite.com/ads.txt anonymously to confirm it returns the plain text, and only then expect serving to begin. If you bought the domain second-hand, delete any inherited records – a line naming the previous owner’s account is worse than an empty file. And remember the file is only one requirement among several: the network also wants real content and the usual policy pages, including a privacy policy and, for any affiliate links, an advertising or affiliate disclosure – see the legal dos and don’ts for what those pages should contain.
A second-hand domain often ships with someone else’s ads.txt, and an inherited seller line fails the check harder than no file at all.
The short version
ads.txt is a public, plain-text file at your domain root that names who is authorized to sell your ad inventory – the ad system’s domain, your publisher account ID, and a DIRECT or RESELLER relationship. Ad networks fetch it before serving and won’t monetize inventory whose file is missing, 404ing, or naming the wrong account, so it’s a frequent silent blocker on a new site. Put the file at /ads.txt, confirm it returns 200 as plain text when you load it anonymously, use the exact record the network gives you, clear out any records inherited with a second-hand domain, and treat it as a launch gate alongside your content and policy pages.
Frequently Asked Questions
What is ads.txt?
It’s a plain-text file – Authorized Digital Sellers – served at a site’s domain root that lists which advertising systems may sell that site’s ad inventory. Each line names an ad system’s domain, the site’s publisher account ID on it, and a DIRECT or RESELLER relationship. Ad networks read it to confirm a seller is genuinely authorized.
Where do I put the ads.txt file?
At the domain root, reachable as https://yoursite.com/ads.txt, returning HTTP 200 as plain text. It must not sit in a subfolder or behind a redirect – the crawler checks exactly that one path. A subdomain generally needs its own file on that host.
Is it a problem that ads.txt is publicly visible?
No – being public is the point. The publisher account ID in the file is an identifier meant to be published, not a secret. Public visibility is exactly what lets any ad buyer verify, independently, that a listed seller is really allowed to sell your inventory.
Why won’t my ad network serve ads even though the site is approved?
A common cause is ads.txt: if the file is missing, returns a 404, or doesn’t list the network with your correct account ID and relationship, the network treats the inventory as unauthorized and holds back. Load the file anonymously and confirm the exact record the network gave you is present and returns 200.
I bought a used domain – do I need to change ads.txt?
Yes. A second-hand domain often carries the previous owner’s ads.txt records, which name an account that isn’t yours. Those are wrong claims and will fail verification. Remove the inherited lines and publish only the records for your own accounts.
