ads.txt File: What It Is and How to Set It Up

What is an ads.txt file?

ads.txt stands for Authorized Digital Sellers. It is an open standard from IAB Tech Lab, the technical arm of the Interactive Advertising Bureau, introduced in 2017. The current ads.txt version 1.1 dates from 2022 and added the OWNERDOMAIN and MANAGERDOMAIN variables.

Picture a guest list at the door: you publish it on your own domain, which proves the owner wrote it, and any seller not on it can be turned away. The idea comes from robots.txt.

Ad exchanges, supply side platforms and buyers are the readers. Each one reads the file before trading inventory that claims to sit on your site. Search crawlers ignore it, and apps use a sibling file, app-ads.txt.

Why ads.txt matters if you show ads

Ad fraud such as domain spoofing is the reason the standard exists. Fraudsters sell counterfeit inventory labeled with your domain, and buyers pay for traffic you never received. A public list lets a buyer skip unauthorized sellers in programmatic advertising and header bidding.

The revenue link shows in Google AdSense. Each site gets an AdSense ads.txt status of Not found, Unauthorized or Authorized, and an alert asks you to fix the file so ad revenue is not affected. Google calls the file not mandatory but highly recommended, and Google Ad Manager publishers use the same file.

Search engines do not read it, so it carries no ranking weight. If you run a blog, our SEO tools for bloggers page collects the other free checks worth running.

How SEO Site Checker tests your ads.txt file

The check asks one question about one address.

The rule: our report sends one HTTPS request to /ads.txt on the host you tested and passes the check only when the final response, after redirects, has status 200.

What the report requests

The request is a single GET to https://your-host/ads.txt with the user agent "Mozilla/5.0 (SEO Checker Bot)". It gives the server 3 seconds to connect and 3 seconds to send data, verifies the certificate and follows redirects. The host is the one you typed, so www and non www count as separate sites.

Pass, warning and fail in our report

Warning and fail print identical wording and show the same How to Fix button, and only the icon color differs. A 401 or 403 therefore means the file may exist but our bot was refused. On Cloudflare, check bot fight mode, challenge pages and firewall rules for a block on /ads.txt. A security plugin or leftover basic auth can do the same, and your own browser may get through where our bot does not.

The result also feeds the overall score, so a site with no ads loses a small share for a file it does not need. If you show no ads, publish the placeholder record from the format section: it is the standards-correct way to say no seller is authorized, and it turns the check green.

What the check does not look at

It never reads the content, so it cannot catch bad syntax or mismatched account lines. An empty file passes, and so does a soft 404 page that answers 200. Open the URL yourself, and run the lines through an ads.txt validator from your ad partner.

ads.txt format: how each line is written

Each record is one line with up to four comma separated fields: the ad system domain, your publisher account ID, the relationship and an optional certification authority ID such as a TAG ID. The third field says how you relate to that ad system: DIRECT means you control the account, RESELLER means you let another company sell your space through its own account. The field is not case sensitive, so direct and DIRECT mean the same thing.

# ads.txt example: replace every value with your partner's lines
google.com, pub-0000000000000000, DIRECT, f08c47fec0942fa0
adexchange.example, 12345, RESELLER
CONTACT=ads@example.com
OWNERDOMAIN=example.com

Lines starting with # are comment lines that ad systems ignore. The zeros stand in for a real ID. Variables such as the CONTACT variable go on their own lines as NAME=value, usually at the end. The specification also defines SUBDOMAIN, MANAGERDOMAIN and INVENTORYPARTNERDOMAIN.

A site that authorizes nobody can publish one placeholder record: placeholder.example.com, placeholder, DIRECT, placeholder. An empty file no longer counts for that purpose. Save as plain text UTF-8. The IAB Tech Lab ads.txt specification holds the full rules.

The companion file is sellers.json, which each ad system publishes itself so buyers can match your lines against its own seller list. Together the two files let buyers check the supply chain behind an OpenRTB bid. It now carries the certification identifiers too, and the specification warns the fourth field may be dropped later, so leave it empty unless a partner gives you the exact ID.

How to create and add an ads.txt file to your website

You do not need an ads.txt generator, because the file is plain text and your ad partners hand you the lines.

Create, upload and confirm

1. Copy the lines. Take them from each ad partner dashboard, where AdSense offers the line ready to copy.
2. Save a text file. Paste one record per line into a plain text editor and save as ads.txt. Avoid Word files and the name ads.txt.txt.
3. Upload to the root. Upload ads.txt to the root directory of the host, usually public_html, so the address is https://yourdomain/ads.txt.
4. Open the address. In a private window, confirm plain text appears.
5. Wait for the recrawl. Google says a few days, or up to a month for sites with few ad requests. To ask for a sooner recheck, open the site under Sites in AdSense and choose Check for updates.

The Google AdSense ads.txt guide explains each status.

Platform notes

• Self-hosted WordPress. Upload ads.txt to the folder that holds wp-content and wp-admin through your host's file manager or SFTP. With a plugin instead, delete any physical ads.txt first, because the two can clash. On WordPress.com you usually cannot reach the root folder, so look in the site's ad settings first.
• Blogger. Open Settings, then Monetization, switch on custom ads.txt and paste your lines.
• Wix. In the site dashboard open Marketing Integrations, find the Ads.txt section and select Connect, then Add ads.txt, paste your lines and save.
• Shopify. There is no root folder, so this is a workaround, not an official feature. Upload the file under Settings, Files, copy its URL, then create a redirect under Online Store, Navigation, URL Redirects from /ads.txt to that URL. The file sits on a different root domain, so it must not redirect again.
• Squarespace. It documents no root upload either, so upload the file as a file link and add a URL Mapping from /ads.txt to its path, for example with a 301. Menu names change, so recheck them.
• Static hosts. On Netlify or Cloudflare Pages, put the file in the folder your build publishes as the site root.

How to check that your ads.txt file works

Open the ads.txt location in a private window for the www and non www versions.

curl -I https://yourdomain/ads.txt

HTTP/2 200
content-type: text/plain; charset=utf-8

Expect status 200 and a text/plain content type, ideally with charset=utf-8. The MDN Content-Type header reference explains the header. The specification says ad systems should treat any other content type as an error and ignore the file, so an HTML error page or a download header will make the file useless even when the lines are correct.

If HTTPS fails, read our SSL and HTTPS test guide. Then run our free report and compare its ads.txt row with the status in your ad partner's dashboard.

Common ads.txt problems and how to fix them

ads.txt vs robots.txt, app-ads.txt and sellers.json

Our robots.txt generator builds the crawler file and what a robots.txt file is explains its rules.