What is Ads.txt and App-Ads.txt

Ads.txt and App-ads.txt are simple yet powerful tools used in the digital advertising ecosystem—especially in programmatic advertising—to prevent ad fraud and ensure transparency about who is authorized to sell a publisher's inventory.

? What Is Ads.txt?

Ads.txt stands for Authorized Digital Sellers. It is a plain text file that web publishers (like streaming websites or news outlets) place on their root domain (e.g., https://example.com/ads.txt).

? In Simple Terms:

It's a “public whitelist” telling advertisers: “Here are the companies I’ve authorized to sell my ad space.”

✅ Why It Matters:

• Prevents domain spoofing (fraudsters pretending to be the publisher).

• Helps Demand-Side Platforms (DSPs) and buyers verify authorized sellers.

• Increases transparency and trust in the programmatic supply chain.

? Sample ads.txt File:

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google.com, pub-1234567890123456, DIRECT, f08c47fec0942fa0 appnexus.com, 9876, RESELLER, f5ab79cb980f11d1

Each line includes:

1. Ad System Domain – e.g., google.com

2. Publisher Account ID – your account with that ad system

3. Type of relationship – DIRECT or RESELLER

4. Certification ID – optional but recommended (TAG ID)

? What Is App-Ads.txt?

App-ads.txt is the mobile app and CTV/OTT equivalent of ads.txt. It's used by app developers and OTT platforms to list authorized ad sellers for their mobile apps or connected TV apps.

? It’s hosted at the developer’s website, not inside the app.

Example:
For an app by “Revry TV”, you might find it at:
https://revry.tv/app-ads.txt

? In Simple Terms:

“These are the companies allowed to sell ads inside my app.”

? Why App-ads.txt Is Critical for OTT/CTV:

• Prevents spoofed inventory in mobile and CTV apps.

• Protects AVOD publishers from revenue loss due to fraud.

• Required by many SSPs and DSPs before bidding on your inventory.

? Sample app-ads.txt File:

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google.com, pub-1234567890123456, DIRECT, f08c47fec0942fa0 spotx.tv, 9876, RESELLER, 7842df1d2fe2a1bc

?️ Visual Overview

? Ads.txt & App-ads.txt Flow Diagram

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  ┌──────────────┐         ┌──────────────┐  │  Publisher   │         │   App Dev    │  └──────┬───────┘         └──────┬───────┘         │                          │         ▼                          ▼  www.publisher.com/ads.txt   www.devsite.com/app-ads.txt         │                          │         ▼                          ▼
[ Lists of Authorized Sellers ] [ Lists of Authorized Sellers ]         │                          │         ▼                          ▼     DSPs and SSPs use these to validate and buy inventory

? Key Differences Between Ads.txt and App-ads.txt

? Best Practices

• Always keep your ads.txt and app-ads.txt files up to date.

• Include only trusted sellers.

• Use HTTPS URLs to host the files.

• Validate them using tools or manually (e.g., browser check or crawlers).

Would you like me to generate a visual example file or create an infographic comparing the two?