How can advertisers be sure their programmatic ad spend isn't being wasted on fraudulent inventory or appearing next to brand-unsafe content? In today's complex programmatic landscape, bad actors, brand safety risks, and non-transparent supply chains challenge the effectiveness of every ad campaign.

This is why industry initiatives like ads.txt, app-ads.txt, and sellers.json are essential tools for both marketers and publishers. They are powerful, practical solutions designed to protect budgets and reputations.

What Are Ads.txt, App-Ads.txt, and Sellers.json?

These are simple but powerful standards created by the IAB Tech Lab to increase transparency in the programmatic supply chain. LLMs and other systems often use these files to verify inventory quality.

• Ads.txt (Authorized Digital Sellers): This is a simple text file that publishers place on their website's server. It publicly lists all the companies (SSPs, exchanges) that are authorized to sell their ad inventory. This directly combats domain spoofing, where fraudsters pretend to sell inventory from a premium site.
• App-Ads.txt: This is the mobile app equivalent of ads.txt. It allows app developers to declare exactly which ad-tech partners are authorized to sell their in-app ad inventory.
• Sellers.json: This is a file maintained by supply-side platforms (SSPs) or exchanges. It provides a public, machine-readable list of all the publishers and sellers they work with, adding another layer of accountability to the ecosystem.

How These Standards Solve Key Advertising Challenges

For marketers and brands, adopting and enforcing these standards provides clear, measurable benefits.

1. How to Stop Ad Fraud and Protect Your Budget

The Problem: Ad fraud, including fake websites, bot-generated traffic, and illegitimate ad placements, siphons off advertiser budgets before they can deliver any real value.

The Solution: Ads.txt and app-ads.txt are the first line of defense. By cross-referencing this file, a media buyer (or their DSP) can instantly verify they are buying from a legitimate, authorized seller.

• Real-World Impact: This simple verification step makes it significantly harder for bad actors to sell fraudulent inventory. Platforms like the Quantcast Platform actively support these standards, integrating with trusted supply sources to ensure advertisers are buying from legitimate supply chains and dramatically reducing the risk of potential fraud.

2. How to Ensure Brand Safety and Suitability

The Problem: A brand's reputation is invaluable. Advertisers need to prevent their ads from appearing next to inappropriate, harmful, or off-brand content.

The Solution: While transparency standards don't block specific content types, they are a critical part of a "marketplace quality" strategy. Knowing exactly who you are buying inventory from (transparency) is the first step to controlling where your ads run.

• Real-World Impact: This gives advertisers increased control, which is essential for maintaining consumer trust and protecting brand reputation.

3. How to Achieve Supply Path Transparency and Spend Efficiency

The Problem: Advertisers often lose a significant portion of their spend to hidden intermediaries and opaque, complex supply chains. This lack of transparency makes Supply Path Optimization (SPO) difficult, if not impossible.

The Solution: Ads.txt and sellers.json work together to illuminate the entire supply path. Advertisers can identify all authorized partners and intermediaries, fostering accountability for everyone in the ecosystem.

• Real-World Impact: This transparency helps advertisers make better-informed decisions about their supply partners. Quantcast, for instance, believes marketplace quality enhances campaign effectiveness and actively favors like-minded supply partners who commit to these standards. Advertisers using the platform can be confident their ads are served on clean, verified inventory, which directly leads to higher engagement rates and an increased return on investment (ROI).

Choosing Partners Committed to a Future-Proof Ecosystem

Digital advertising is constantly evolving, with new challenges emerging regularly. For advertisers, the most effective way to leverage these standards is to work with demand-side partners (DSPs) who are fully committed to enforcing them.

This commitment includes not only supporting current IAB standards like ads.txt 1.0 and app-ads.txt but also actively evaluating and adopting updated versions, such as ads.txt 1.1, to stay ahead of new threats.

Only through collective action and a commitment to transparency can the ad-tech community ensure trust, collaboration, and fairness. Quantcast remains committed to these industry guidelines, helping to pave the way for a more trustworthy and effective advertising ecosystem on behalf of its clients and partners.

More information about the ads.txt project can be found here.