ads.txt Validator

Check your ads.txt file for the errors that stop advertising systems reading it. Enter a domain and every malformed record, duplicate and typo is listed by line number.

SEO Audit Any Site in Seconds
+ Comprehensive SEO / GEO Tools for Every Function

Run over 100 checks on your website across On-Page SEO, Usability, Performance, Social and Links. Now with GEO in every report. SEOptimer also offers keyword research, rank tracking, backlinks and a full site crawler.

Inizia la Prova Gratuita di 14 Giorni

About ads.txt

What is ads.txt?

ads.txt is a plain text file at the root of your domain listing every company allowed to sell your advertising inventory. It stands for Authorized Digital Sellers, and it has been an IAB Tech Lab standard since 2017.

It exists to stop a specific fraud. Before it, anyone could offer ad space claiming to be your site, and a buyer had no way to check. Publishing the file means a buyer can verify that whoever is selling your inventory is somebody you actually authorised.

Anyone can read yours, and you can read anyone else's - it is public by design, since a file only buyers could see would be no use.

Why AdSense keeps warning you about it

Most people meet ads.txt through a message in AdSense saying "Earnings at risk - you need to fix ads.txt file issues". That warning is the reason this ads.txt checker exists.

It appears when Google cannot find the file, cannot read it, or cannot find its own line inside it. Any of the three leaves your inventory looking unauthorised, and buyers who enforce the standard will simply not bid.

The fix is usually small - a missing file, a typo in one line, or a server returning the wrong content type. Running an ads.txt checker before you start guessing tells you which of those it is.

What a record looks like

Each line names one seller, as three or four comma separated fields:

The advertising system's domain, such as google.com - a domain, never a full URL.
Your publisher account ID with that system, exactly as they issue it.
DIRECT if you hold the account yourself, RESELLER if somebody sells on your behalf.
Optionally, the seller's certification authority ID - a TAG ID of 16 hexadecimal characters.

Lines starting with # are comments, and a handful of variables are allowed, of which OWNERDOMAIN and MANAGERDOMAIN are the ones most sites use.

What this ads.txt checker looks for

The validator fetches the file from your domain root and reads it line by line, separating what actually breaks a record from what is merely untidy.

Records with too few or too many fields, which are skipped entirely.
A relationship that is not DIRECT or RESELLER.
A full URL where the advertising system's domain belongs.
Empty account IDs, duplicated records and malformed certification IDs.
Curly quotes and dashes, which mean the file was edited in a word processor.
A file served as HTML rather than text/plain, or a byte order mark on line one.

Every finding is reported with its line number, so the ads.txt checker tells you where to look rather than that something is wrong somewhere.

What no checker can tell you

This validator confirms your file says what you meant it to say. It cannot confirm that what you meant is true: only the advertising system knows whether an account ID really belongs to you, so a perfectly valid file can still name a relationship that does not exist.

Nor can it tell you a line is missing. A file listing one network is valid; it just fails to authorise all the others, and the symptom shows up as unsold inventory rather than as an error.

If a network is warning you specifically, check that its own line is present and that the account ID matches the one in your account with them, character for character.

Does ads.txt affect SEO?

No. It is monetisation plumbing - search engines do not read it, and it has no bearing on how a page ranks. Anyone telling you otherwise is selling something.

It sits in a toolbox like this one for the same reason DNS and mail records do: it lives at your domain, it breaks quietly, and the person who has to fix it is usually the person who looks after the site.

The indirect connection is money rather than rankings. A broken file costs advertising revenue, and that tends to be noticed long after it started.

Where to go next

ads.txt has a companion, app-ads.txt, which does the same job for mobile apps and lives at the developer website root - paste that address into the ads.txt checker above and it will be validated the same way.

For the rest of what lives at your domain root, check what crawlers are allowed with the robots.txt tool, confirm your mail records with the SPF and DMARC checks, and see the whole picture with a full site audit.

Comprehensive SEO Toolbox with over 55 Tools

Check Titles, Meta Descriptions, Headings, Schema, Core Web Vitals, SSL and Robots.txt. Generate Meta Tags, Sitemaps and .htaccess Rules, minify CSS, JS and HTML, and draft copy with our AI Writing Tools - instantly and for free.