How does… ads.txt work?

In a new feature for Mumbrella, some of the industry's most knowledgable boffins break down industry jargon to help you through those confusing meetings and indecipherable conferences. This week, IAB Australia's Jonas Jaanimagi explains how ads.txt works.

What is it?

Ads.txt is a solution developed by IAB Tech Labs in 2017 as a way to increase transparency in the programmatic advertising space.

The ‘ads’ part stands for Authorised Digital Sellers and “txt” means, well, text. It is a text file that is hosted on a site’s domain declaring that it’s an authorised seller. It was invented to prevent criminals from monetising misleading ad opportunities via domain spoofing.

Need the simpler version please

There are some bad actors online who pretend to be someone else in order to make money from digital advertising (aka domain spoofing).

For example, one of these bad actors might be offering ad space on a sub-standard site – such as a conspiracy theory chat room – but be representing that space as if it were on a popular news site. Essentially, they are pretending to be a legitimate site when they aren’t. They do this by masking the identity of the URL in the programmatic bid stream.

Ads.txt was invented to stop them. If the good guys put the ads.txt text file on their website domain, it shows who the legitimate seller is – this means the bad actors can’t pretend to be anyone that they are not.

Got it. Is it easy to use?

Yes. It’s easy to put the file on a domain which you own; which in turn makes it easy for buyers of programmatic inventory to quickly and easily identify which sellers are whitelisted (aka authorised) to sell the inventories for certain publishers.

Think of it as a digital handshake between the publisher and an exchange that signifies a legitimate connection. The buyer can check to see if the correct parties are shaking hands, and if so, can be confident that the inventory they are buying will actually appear in the place they wish it to appear.

Hit me with some more of the tech stuff (less techie folk should skip to ‘Is it working?’)

A publisher will install the ads.txt text file on their root domain (or any necessary sub-domains), listing all the platforms, ad-exchanges or supply-side platforms (SSPs) sanctioned to directly or indirectly sell their inventory. Each listing on the root domain includes the publisher’s “seller account ID” for that particular SSP, which links it to that publisher’s account on that SSP.

The data needed to populate the file is available in OpenRBT protocols, making it easy to gather and target. In the programmatic bidding process, this publisher ID is transmitted through OpenRTB protocols as the “SellerAccountID” along with the publisher’s domain and the list of authorised sellers. It makes more sense if you consider the below example.

Demand-side platforms (DSPs) can crawl the web for ads.txt files and create a list of sellers authorised to handle inventory for specific publishers or domains. That list can then be used to create a filter that checks your ads.txt list with the data from OpenRBT bid requests. Matching IDs signal that the exchange or SSP is a sanctioned seller for that publisher.

The process is outlined in the infographic below.

Is it working?

Yes. Adoption of ads.txt got off to a sluggish start but it’s beginning to accelerate both globally and locally (it was given a boost when big companies like Google, AppNexus and a number of large marketers also got on board).

The latest global data from Pixalate published in January 2018, tells us that of the top 5,000 sites globally, 45.2% have implemented the ads.txt solution. When it hits critical mass (expected soon), ads.txt will all but eliminate domain spoofing – thus dramatically reducing globally the levels of fraud in programmatic advertising.

Jonas Jaanimagi is technology lead at IAB Australia. For more information on ads.txt click here.


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