The ads.txt file (Authorized Digital Sellers) is one of the most underutilized sources of competitive intelligence on the web. Required by the IAB Tech Lab for programmatic advertising transparency, this publicly accessible file at /ads.txt lists every SSP (Supply-Side Platform) and ad exchange that a publisher has authorized to sell their advertising inventory. For OSINT analysts, competitive researchers, and ad tech professionals, ads.txt is a window into a website's monetization strategy.
What ads.txt Reveals
Each line in an ads.txt file follows a standard format: domain, account_id, relationship, certification_id. This structured data reveals:
- SSP relationships: Which ad exchanges the publisher works with (Google AdX, Xandr, Index Exchange, OpenX, Pubmatic, etc.)
- Direct vs. reseller: Whether the publisher has a direct relationship with the SSP or sells through a reseller, indicating their scale and ad ops sophistication
- Account identifiers: The publisher's account ID on each platform, which can be used to find other domains using the same account
- Monetization scale: A site with two SSPs has different monetization than one listing twenty-plus exchanges with header bidding wrappers
Competitive Intelligence from ads.txt
Analyzing ads.txt files across competitors reveals industry patterns. You can determine which SSPs dominate a vertical, identify publishers that have recently added or removed ad partners, and spot trends in programmatic advertising adoption. The account IDs in ads.txt can also link together properties owned by the same publisher network, revealing corporate relationships that may not be publicly documented.
For ad tech companies, ads.txt intelligence reveals market penetration. If your SSP appears in fewer ads.txt files than a competitor, that is a clear signal about market share. Tracking ads.txt changes over time shows which platforms are gaining or losing publisher partnerships.
OSINT Applications
From an OSINT perspective, ads.txt data is powerful for network analysis. Shared account IDs across domains can reveal publisher networks and corporate ownership structures. The presence of specific ad tech vendors can indicate geographic focus (regional SSPs) or content category (adult content exchanges, gaming-specific platforms). Fraud investigators use ads.txt to identify unauthorized reselling and domain spoofing in the programmatic supply chain.
Automated ads.txt Analysis with WhatStack
WhatStack's OSINT capabilities include a dedicated ads.txt analyzer that fetches and parses the ads.txt file as part of every scan. The results identify all SSPs and ad exchanges, categorize them, and include them in the technology profile alongside the site's other technologies.
This means a single WhatStack scan reveals not just the website's application stack (CMS, frameworks, analytics) but also its complete advertising technology ecosystem. For ad tech sales teams, this is a powerful prospecting tool. For OSINT analysts, it adds another data layer to the technology fingerprint. Explore WhatStack for OSINT to learn more about using ads.txt and other signals for website intelligence.