In this article we answer the question: “What is app-ads.txt?” We provide examples, use cases, and definitions for app-ads.txt, ads.txt, and sellers.json. We also explain how to set up app-ads.txt for your apps.

Mobile and connected TV (CTV) advertising has exploded in recent years. In 2024, experts anticipate that some $400 billion will be put towards mobile ads globally. If so, that would mark an 11% year-on-year increase from 2023. Likewise, CTV advertising is among the fastest growing ad mediums in the world, with annual spend expected to reach $25.9 billion globally in 2023, up 13.2% YOY.

However, with all that money changing hands, bad actors have taken notice. According to some, digital ad fraud will cost businesses upwards of $84 billion in 2023 alone.

Fortunately, there are steps businesses in the mobile and CTV ad industry can take to mitigate these malicious actors. One such step is to proactively leverage the Interactive Advertising Bureau’s (IAB) app-ads.txt, ads.txt, and sellers.json standards to prevent fraud.

To help out, we’ve written this article introducing you to app-ads.txt. Here’s what we cover:

• • What Is App-ads.txt?
• • How to Add App-ads.txt to Your App
• • What Is Ads.txt?
• • What Is Sellers.json?
• • App-ads.txt versus Ads.txt versus Sellers.json
• • Why Is App-ads.txt Important? The Benefits and Uses of App-ads.txt
• • How Can Companies Use App-ads.txt?
• • App-ads.txt Use Cases for App Developers and Publishers
• • App-ads.txt Use Cases for Advertisers
• • App-ads.txt Use Cases for Ad Networks and Exchanges
• • App-ads.txt Use Cases for Ad Verification Companies
• • App-ads.txt Use Cases for Programmatic Platforms
• • Get Easy Access to App-ads.txt Insights

Ready to get started? Try our IAB Category APIs and file dumps.

What Is App-ads.txt?

App-ads.txt is a standard developed by the Interactive Advertising Bureau Tech Lab (IAB Tech Lab) to increase transparency in the mobile advertising ecosystem to combat ad fraud. It enables demand-side platforms (DSPs) to acquire ad space from authorized suppliers by allowing app publishers to declare which companies are authorized to sell their ad inventory.

Here’s how it works. App-ads.txt is a text file that lists all ad sources authorized to sell an app’s inventory. App publishers place this text file on their website so DSPs that bid on app inventory can be confident that the ad sources they work with are authorized to sell an app’s inventory.

Key points about the IAB Tech Lab’s app-ads.txt standard:

• App-ads.txt Purpose: The primary purpose of app-ads.txt is to provide a mechanism for app developers to declare who is authorized to sell their digital advertising inventory. By doing so, it helps prevent unauthorized inventory sales.

• How App-ads.txt Works: App developers create a simple, publicly accessible app-ads.txt file and host it on their website. This file lists the ad networks, exchanges, and other entities authorized to sell the app's ad inventory. Programmatic platforms can then crawl and check these files to ensure they only buy inventory from authorized parties.

• Combatting Ad Fraud with App-ads.txt: One of the challenges in the mobile advertising ecosystem is the prevalence of domain spoofing and unauthorized reselling. Bad actors can misrepresent their traffic as coming from a legitimate or more popular app to get higher ad rates. By implementing app-ads.txt, app developers can specify which entities can sell their inventory, making it harder for fraudsters to profit from unauthorized sales or spoofing.

To make their app-ads.txt scanning processes more efficient, DSPs can also use third-party solutions to view aggregated app-ads.txt data. For example, at 42matters, we provide app-ads.txt insights for 20+ million published and unpublished apps via our app-ads.txt API, app-ads.txt file dump, and the 42matters Explorer platform. These offer insight into app-ads.txt files for iOS and Android apps and connected TV (CTV) apps available on Roku, Apple TV, Fire TV, Google TV, Samsung TV, LG TV, and Vizio.

How to Add App-ads.txt to Your App

Leveraging app-ads.txt to prevent ad fraud on your app involves several steps, primarily focused on creating the file and making it publicly accessible on your app's associated website.

Here's a quick step-by-step guide for how to set up app-ads.txt for your apps:

1. 1. Create the File: Open a plain text editor (like Notepad on Windows or TextEdit on Mac) and list the ad inventory sellers authorized to place ads on your apps. Each line should contain the domain name of the seller, the publisher's account ID, the type of relationship (DIRECT or RESELLER), and an optional certification authority ID.

1. 2. Host the File on Your Website: The app-ads.txt file should be placed at the root of your app's associated website. For instance, if your app's website is example.com, the app-ads.txt file should be accessible at https://example.com/app-ads.txt. Ensure the file is publicly accessible and can be crawled by ad platforms and exchanges.

1. 3. Update Your App Store Listings: For the app-ads.txt file to be effective, ad platforms need to know where to find it. This is done by associating your app with its official website. You can do this on Google Play by updating the "Website" field in your app's store listing with the URL of your official website. For the App Store, ensure that your app's listing includes the domain where the app-ads.txt file is hosted.

1. 4. Regularly Update the File: As you form new partnerships or change ad networks/exchanges, update the app-ads.txt file accordingly. Remove entities no longer authorized to sell your app's ad inventory.

1. 5. Inform Your Partners: Let your ad partners, networks, and exchanges know you've implemented app-ads.txt. This can help ensure they're aware and can validate against your file.

1. 6. Stay Updated: The IAB Tech Lab, which introduced the app-ads.txt standard, may release updates or best practices over time. Stay informed to ensure your implementation remains compliant.

What Is Ads.txt?

Before we look at the benefits and uses of app-ads.txt, we’d like to clarify a few things. Specifically, we’d like to define ads.txt and sellers.json, two standards similar to app-ads.txt.

Let’s begin with ads.txt. Short for Authorized Digital Sellers, ads.txt is another standard designed by the IAB Tech Lab to increase transparency in the programmatic advertising ecosystem and combat certain types of ad fraud. Like app-ads.txt, it allows digital publishers to clearly state who can sell their ad inventory. It thereby aims to reduce the impact of ad fraud and ensure that ad spend reaches legitimate and intended destinations.

In fact, app-ads.txt is an extension of ads.txt. We’ll go into a little more detail on this in a moment, but it’s essential to know that while app-ads.txt was explicitly designed for mobile apps, ads.txt was designed for the digital space more broadly.

Key points about the ads.txt:

• Purpose: The primary goal of ads.txt is to provide a mechanism for digital publishers to publicly declare the companies they authorize to sell their digital ad inventory. Doing so helps prevent unauthorized inventory sales, such as domain spoofing and counterfeit inventory.

• How It Works: Publishers create a simple, publicly accessible ads.txt file and host it on their domain. This file lists the ad networks, exchanges, and other entities authorized to sell the publisher's ad inventory. Advertisers and programmatic platforms can then crawl and check these files to ensure they only buy inventory from authorized parties.

• File Format: Like app-ads.txt, ads.txt files contain lines of data, each representing an authorized seller. Lines typically include the domain name of the seller, the publisher's account ID with that seller, the type of relationship (DIRECT or RESELLER), and an optional certification authority ID.

• Combatting Ad Fraud: One of the challenges in the digital advertising ecosystem is the prevalence of domain spoofing, where bad actors misrepresent their traffic as coming from a legitimate or more popular website to get higher ad rates. By implementing ads.txt, publishers can specify which entities can sell their inventory, making it harder for fraudsters to profit from unauthorized sales or spoofing.

What Is Sellers.json?

Sellers.json is another related initiative by the IAB Tech Lab to enhance transparency in the programmatic advertising ecosystem.

While ads.txt and app-ads.txt focus on the publisher side, sellers.json provides transparency from the supply-side platform (SSP) or exchange side. Put plainly, it enables ad space buyers to discover and verify the entities selling digital ad space, whether they’re the direct sellers or intermediaries.

Key points about the ads.txt:

• Purpose: The primary goal of sellers.json is to allow buyers to verify the entities involved in selling digital advertising inventory. It allows SSPs and exchanges to declare information about their publisher partners publicly.

• How It Works: SSPs and exchanges create a sellers.json file and host it on their domain. This file lists information about all the publishers and intermediaries they work with, including publisher IDs, types of relationships (whether they're direct sellers or intermediaries), and more. Advertisers and programmatic platforms can then access these files to verify the entities they buy inventory from.

• Combatting Ad Fraud: Sellers.json complements ads.txt and app-ads.txt by providing an additional layer of transparency. While ads.txt allows publishers to declare who is authorized to sell their inventory, sellers.json allows buyers to verify the entities they transact with on the SSP or exchange side. This dual verification mechanism makes it even harder for bad actors to engage in unauthorized sales or misrepresentation.

• File Contents: The sellers.json file contains entries for each publisher or intermediary with which the SSP or exchange works. Each entry typically includes: SellerId, seller name, seller domain, seller type ("PUBLISHER" or "INTERMEDIARY"), directness ("DIRECT" or "RESELLER"), and other optional fields like certification authority ID.

App-ads.txt versus Ads.txt versus Sellers.json

App-ads.txt, Ads.txt, and Sellers.json are all initiatives introduced by the IAB Tech Lab to enhance transparency and combat fraud in the programmatic advertising ecosystem. While they serve related purposes, each has a distinct focus and function.

Here are the key differences between app-ads.txt, ads.txt, and sellers.json:

While ads.txt and app-ads.txt are publisher-centric, allowing publishers and app developers to declare who can sell their inventory, sellers.json is SSP/exchange-centric, allowing these platforms to declare information about their publisher partners and intermediaries.

In addition, while ads.txt is for web-based content, app-ads.txt is for mobile app publishers, and sellers.json is for SSPs and exchanges.

Finally, all three aim to combat ad fraud but do so in different ways. While ads.txt and app-ads.txt focus on preventing unauthorized sales from the publisher's side, sellers.json provides SSP or exchange-side transparency.

Read our report on the state of app-ads.txt and sellers.json.

Why Is App-ads.txt Important? The Benefits and Uses of App-ads.txt

App-ads.txt is essential for several reasons, primarily centered around enhancing transparency, trust, and security in the mobile and connected TV (CTV) advertising ecosystems. So, let’s look at some of the benefits and uses of the app-ads.txt standard.

App-ads.txt Benefits

Turning first to the benefits, let’s look at how app-ads.txt can be used to…

• • Combat Ad Fraud
• • Protect Ad Revenue
• • Build Trust with Advertisers
• • Foster Transparency
  

Combat Ad Fraud

The primary value of app-ads.txt is that it helps combat ad fraud in the mobile and connected TV (CTV) domains. It does this by reducing the impact of things like unauthorized sales and domain spoofing. Indeed, without mechanisms like app-ads.txt, bad actors can sell ad inventory on behalf of apps without the app developer's permission. This unauthorized selling can lead to revenue loss for legitimate publishers. Likewise, fraudsters can misrepresent their traffic as coming from a legitimate or popular app, tricking advertisers into paying premium rates for low-quality or non-existent traffic.

Protect Ad Revenue

Ad fraud hurts revenue — for app publishers, SSLs, DSLs, advertisers, and pretty much everyone involved in the mobile / CTV advertising space.

By specifying authorized sellers via app-ads.txt files, app developers can ensure that advertisers spend their budgets on legitimate inventory. This helps them maintain and grow ad revenue, guarantee quality ad impressions for advertisers, and uphold their reputation in the market.

Moreover, it prevents the dilution of ad revenue that might occur if unauthorized parties were selling their app's inventory at lower rates or in ways that violate the app's policies.

Build Trust with Advertisers

Unsurprisingly, advertisers want to ensure their ad spend is directed towards legitimate inventory and reaching their intended audiences. App-ads.txt provides this assurance, making advertisers more confident in allocating budgets toward apps that implement the standard.

Foster Transparency

App-ads.txt provides an explicit public declaration of authorized sellers, making the mobile advertising ecosystem more transparent. Ad platforms, networks, and exchanges can easily verify the authenticity of ad inventory, ensuring they're transacting with authorized parties.

App-ads.txt Uses

Simply put, app-ads.txt serves as a protective shield for app developers, advertisers, and platforms, ensuring a transparent, trustworthy, and secure mobile advertising environment. So, let’s look at some ways app-ads.txt can be used to accomplish this for different stakeholders in the mobile advertising ecosystem.

Here are some of the primary uses for app-ads.txt:

• Verification of Authorized Sellers: Ad platforms, networks, and exchanges can crawl and check app-ads.txt files to verify the authenticity of ad inventory and ensure they are buying from approved sources.

• Monetization Strategy: App developers can strategically choose and list their preferred ad networks, exchanges, and direct advertisers, giving them more control over their monetization partners.

• Brand Safety Assurance: Advertisers can cross-reference app-ads.txt files to ensure their ads are placed in genuine apps, reducing the risk of their brand being associated with low-quality or inappropriate content.

• Fraud Detection: Ad verification companies and anti-fraud solutions can use app-ads.txt to detect discrepancies in ad inventory sales, helping identify and mitigate potential fraud.

• Compliance and Reporting: Some ad platforms may provide reports or tools to help app developers verify their app-ads.txt implementation, ensuring it's correctly set up and compliant with industry standards.

Here are more ways ad tech companies can enhance their mobile advertising strategy.

How Can Companies Use App-ads.txt?

Companies can utilize app-ads.txt in various ways, depending on their role in the mobile advertising ecosystem. Here's a breakdown of how different entities can use app-ads.txt:

• • App Developers and Publishers
• • Advertisers
• • Ad Networks and Exchanges
• • Ad Verification Companies
• • Programmatic Platforms
  

App-ads.txt Use Cases for App Developers and Publishers

First and foremost, app developers and publishers use app-ads.txt to authorize digital ad sellers. This entails creating and hosting app-ads.txt files on their official websites that list all authorized ad networks, exchanges, and direct advertisers.

In addition, app-ads.txt allows developers and publishers to control their monetization strategy by selecting preferred ad partners and ensuring that only trusted and high-performing partners are authorized to sell their ads. This helps publishers optimize ad revenue and prevent ad fraud.

Finally, app-ads.txt facilitates brand protection by enabling developers to reduce the risk of hosting low-quality ads or inappropriate content.

App-ads.txt Use Cases for Advertisers

Next up, let’s look at some use cases for advertisers, beginning with inventory verification. Indeed, before purchasing ad inventory, advertisers can check an app's app-ads.txt file to ensure they buy from authorized sellers, reducing the risk of fraud.

Brand Safety is another big one. By ensuring that their ads are placed in genuine apps, advertisers can reduce the risk of their brands being associated with counterfeit inventory or inappropriate content. Moreover, by perusing app-ads.txt files that list their demand-side partners (ad networks, ad exchanges, etc.), they can identify particular apps they’d like to avoid when it comes to acquiring ad space and request that their partners adjust their programmatic buying decisions accordingly.

Finally, advertisers can use app-ads.txt to improve budget optimization. Advertisers can ensure better ad placements and potentially higher ROI by purchasing inventory from authorized sellers.

App-ads.txt Use Cases for Ad Networks and Exchanges

Turning to other demand-side businesses, ad networks and exchanges can use app-ads.txt to authenticate their inventory. For example, they can cross-reference their own listings with app-ads.txt files to ensure they are authorized to sell inventory on specific apps.

App-ads.txt is also great for helping ad networks and exchanges proactively prevent fraud. They can use it to detect discrepancies or unauthorized sales by regularly checking their authorization status in app-ads.txt files across their publisher partners.

Another way ad networks can use app-ads.txt is to scope out their competition. By reviewing app-ads.txt files, they can see which apps have integrated their competitors’ SDKs and use this information to reverse engineer their strategy for gaining market share. For example, suppose they see that their competitors are gaining traction among Fitness apps, apps based in the United States, or apps that rank in the global top charts. In that case, they can infer their lead generation strategy and adjust their own approach accordingly.

App-ads.txt Use Cases for Ad Verification Companies

Likewise, ad verification companies can use it similarly to detect fraud. Moreover, they can use app-ads.txt to provide reports or insights to clients based on app-ads.txt compliance and implementation across the mobile ad ecosystem.

App-ads.txt Use Cases for Programmatic Platforms

Finally, programmatic platforms can use it to enhance automated verification. They can integrate automated checks for app-ads.txt compliance when facilitating programmatic ad buys, ensuring transactions are made only for authorized inventory.

They can also use it for enhanced filtering. For example, filtering out apps that don't have an app-ads.txt file or have discrepancies in their file can ensure a more secure and transparent buying process for advertisers.

And that’s that! To learn how to access app-ads.txt files easily and at scale, check out our app-ads.txt APIs and file dumps over at 42matters!

Get Easy Access to App-ads.txt Insights

42matters is a leading mobile and connected TV (CTV) app data and app store intelligence provider. Our APIs, file dumps, and visual app market research platforms offer insight into tens-of-millions of mobile and CTV apps from 12 leading app stores. This includes the Apple App Store, Google Play, Amazon Appstore, Tencent Appstore, Huawei App Gallery, Roku Channel Store, Apple TV tvOS App Store, Amazon Fire TV, Google TV, Samsung Smart TV Apps, LG Content Store, and Vizio SmartCast Apps.

If you’re interested in accessing app-ads.txt insights for mobile apps and games check out these file dumps:

• • Google Play: Download App-Ads.txt Gplay Dump Sample
• • The Apple App Store: Download App-Ads.txt iTunes Dump Sample
• • The Amazon Appstore: Download App-Ads.txt Amazon Dump Sample

If you’re curious about connected TV (CTV) apps, you can use the following links:

• • The Roku Channel Store: Download App-Ads.txt Roku Dump Sample
• • The Apple TV tvOS App Store: Download App-Ads.txt tvOS Dump Sample
• • Amazon Fire TV: Download App-Ads.txt FireTV Dump Sample