Ads TXT Checker

What is Ads.txt? The Complete Guide to Fighting Ad Fraud

Look, I'm going to be straight with you. The digital advertising world has a massive problem — and it's called ad fraud. We're talking about $81 billion stolen globally in 2024. That's not a typo. Eighty-one billion dollars. Gone. Vanished into the pockets of fraudsters who figured out how to game the system.

But here's the good news: there's a simple, elegant solution that's been quietly revolutionizing the industry. It's called ads.txt, and if you're running a website or buying digital ads, understanding it is absolutely essential. Think of this page as your crash course — I'm going to explain everything like you're hearing it for the first time.

Ads.txt Explained: The Simple Version

Imagine you're selling concert tickets. Real, legitimate tickets. But suddenly, a bunch of scammers start selling fake tickets to YOUR concert, pocketing the money while your actual fans get ripped off. Nightmare, right?

That's exactly what was happening in digital advertising. Bad actors were pretending to sell ad space on premium websites — The New York Times, ESPN, you name it — when they had zero authority to do so. Advertisers were paying for ads that never appeared on real sites.

Ads.txt (which stands for Authorized Digital Sellers) fixes this. It's a simple text file that publishers put on their website saying: "Hey, THESE are the only companies allowed to sell my ad inventory. Anyone else? They're frauds."

Why Should You Care? The Numbers Don't Lie

I love data. Data doesn't have opinions. It just tells you what's real. And the data on ads.txt adoption is incredibly compelling:

Here's what blows my mind: the digital advertising industry saved $10.8 billion in the US alone by reducing ad fraud in 2023. That's a 92% reduction in potential losses. Ads.txt wasn't the only tool, but it was a critical piece of the puzzle.

How to Read an Ads.txt File (It's Easier Than You Think)

When you analyze a domain using our tool, you'll see entries that look something like this:

Let me break down each part:

• 1
  Exchange Domain (google.com, openx.com) — This is the advertising platform or exchange that's authorized to sell the inventory.
• 2
  Publisher Account ID — The unique identifier for the publisher's account on that exchange. This is crucial for verification.
• 3
  Relationship Type — Either DIRECT (the publisher has a direct deal with the exchange) or RESELLER (another company is authorized to resell their inventory).
• 4
  Certification Authority ID (optional) — Usually a TAG (Trustworthy Accountability Group) ID that adds another layer of verification.

DIRECT vs. RESELLER: What's the Real Difference?

This is where it gets interesting for advertisers. When you see our tool showing the breakdown of direct sellers versus resellers, here's what you're really looking at:

Neither is inherently "bad" — legitimate publishers use both. But if you're an advertiser, understanding this ratio helps you make smarter buying decisions. A site with 90% reseller entries might warrant closer scrutiny than one with mostly direct relationships.

The IAB Tech Lab: The People Behind the Standard

Ads.txt wasn't invented by some random startup. It was developed by the IAB Tech Lab (Interactive Advertising Bureau Technology Laboratory) — the same organization that creates most of the technical standards powering digital advertising globally. These are the folks who brought us OpenRTB, VAST, and dozens of other protocols that make programmatic advertising work.

When ads.txt launched in 2017, adoption was slow. But fast-forward to today, and 65% of ad buyers now require ads.txt or sellers.json compliance before they'll even consider bidding on inventory. That's not just adoption — that's becoming table stakes.

App-Ads.txt: The Mobile Extension

Here's something most people don't realize: mobile apps have their own version called app-ads.txt. Same concept, different implementation.

For mobile apps, the app-ads.txt file lives on the developer's website (the one listed in the app store), not in the app itself. As of late 2024, about 27.29% of apps on Google Play have implemented app-ads.txt — up from 25.91% just months before. The trend is clearly moving in the right direction.

How to Use Our Ads.txt Checker

Using this tool is dead simple. Here's the three-step process:

1. Enter any domain in the search box above (just the domain, no https:// needed)
2. Click "Analyze" and wait a few seconds while we fetch and parse the ads.txt file
3. Review the results — you'll see total entries, direct sellers count, reseller count, and a sample of the actual ads.txt entries

Try it with big publishers like nytimes.com or espn.com — you'll see they often have hundreds or even thousands of authorized sellers. That's normal for major publishers who work with multiple demand partners.

Why This Matters for Publishers

If you're a website owner or publisher, here's the bottom line: not having an ads.txt file is leaving money on the table. Here's why:

• Many DSPs (Demand-Side Platforms) won't bid on inventory without ads.txt verification
• Google Ad Manager, AdX, and most major exchanges now require it
• It protects YOUR brand from being associated with fraudulent inventory
• It's literally a text file — takes 5 minutes to set up

Why This Matters for Advertisers

If you're buying programmatic ads, checking ads.txt should be part of your verification process:

• Always verify that the seller you're buying from is actually authorized
• Look for suspicious patterns (too many resellers, unknown exchanges)
• Use tools like this checker as part of your brand safety workflow
• Consider prioritizing DIRECT relationships for premium inventory