(Image from DigitalAdBlog)
If you're not in the digital advertising industry, you may not be aware of the ads.txt initiative which aims to prevent fraudulent inventory from being purchased by advertisers. It requires publishers to serve an ads.txt file (a simple text file) from their domain that contains a list of all the companies that they've authorized to sell their inventory. Specifically, each line contains the domain of the selling company, the ID of the publisher whose inventory is being sold or re-sold, and whether the publisher is in fact selling the inventory directly or re-selling it. For example, take a site like TMZ. It's ads.txt file is located at http://www.tmz.com/ads.txt. If you look at this file in your browser, you'll see the following entires (at the time of this post):
google.com, pub-2971421842924714, DIRECT, f08c47fec0942fa0
rubiconproject.com, 10794, DIRECT, 0bfd66d529a55807
indexexchange.com, 184128, DIRECT
indexexchange.com, 184534, DIRECT
openx.com, 537118698, DIRECT, a698e2ec38604c6
openx.com, 537150859, DIRECT, a698e2ec38604c6
taboola.com, 624, DIRECT
pubmatic.com, 156296, DIRECT, 5d62403b186f2ace
amazon-adsystem.com, 3064, DIRECT
sharethrough.com, 2fb9d1f3, DIRECT
districtm.io, 100606, DIRECT
appnexus.com, 1908, RESELLER
appnexus.com, 7186, DIRECT
connatix.com, 100283, DIRECT
tremorhub.com, 2g44a-eq9hn, DIRECT, 1a4e959a1b50034a
tremorhub.com, wwmff, DIRECT, 1a4e959a1b50034a
coxmt.com, 2000068019402, DIRECT
The 7th line tells you that TMZ works directly with native ad company Taboola who sells TMZ's ad inventory programmatically to buyers on Demand Side Platforms (DSPs):
taboola.com, 624, DIRECT
The 12th line tells you that the ad exchange AppNexus re-sells TMZ's ad inventory after buying it from some publisher on its platform with ID 1908. From this ads.txt file alone, we cannot tell who it is, but some publishers have put comments in their ads.txt file that reveals this information.
appnexus.com, 1908, RESELLER
DSPs are expected to crawl and ingest the data from all these ads.txt files so that their advertisers can use it to whitelist inventory, checking that the stated seller of the inventory was indeed authorized by the owner of the stated domain.
As you can imagine, there is a lot of interesting data you can find by simply crawling the ads.txt files of various websites. It reveals who works with who in digital advertising. The guy from Ad Ops Insider has done exactly that and published his findings on the State of ads.txt Adoption yesterday.