Ads.txt was one of the key buzzwords in programmatic advertising last year. After slow adoption, take up accelerated during the second half of 2017 fuelled by support from Google and better understanding from publishers of the benefits to them. With scale, it enabled DSPs to start trading programmatically using Ads.txt only buys. The Ads.txt specification an IAB Tech Lab supported initiative.

What problem does Ads.txt solve?

Ads.txt stands for Authorised Digital Seller and it’s a simple way for publishers to publicly state the SSPs that are authorised to sell their ad inventory.

The problem Ads.txt solves is twofold: supply platforms offering access to publisher inventory that had not approved and domain spoofing: fake domains masquerading as publishers.

And Ads.txt is the solution. By providing transparency in the market place via public authorisation that an SSP is allowed to sell that publisher’s ad inventory.

What is the benefit to advertisers?

Ads.txt makes it harder for bad intermediaries to profit from unauthorised selling or domain spoofing because advertisers can now identify authorised digital sellers for a publisher, and bid only on legitimate impressions. In doing so, Ads.txt provides a layer of trust and confidence that advertiser’s are buying legitimate ad inventory. In doing so, Ads.txt can potentially open up more scale to advertisers who have brand safety concerns.

Ads.txt buys should increase the value of programmatic trading because of the benefits of brand safety and ad fraud; advertisers should see improved KPIs as a result.

What exactly is Ads.txt?

As the name suggests, Ads.txt is a file created by DSPs by crawling publisher websites. For every combination of publisher domain and SSP (for example,, Rubicon;, Teads;, SpotX), the crawler records whether the domain and SSP relationship is either “direct” or “reseller”. Where the publisher has not yet adopted ads.txt, it is flagged as “not verified”.

The file can be regularly updated by mobile DSPs so that campaigns can access the most recent version of events.

Source: Adnimation

Are there any limitations to campaign delivery?

Scale: While Ads.txt is gaining traction, there are still publishers that do not support it. For now, scale may limit some inventory options.

Ad fraud: Ads.txt alone does not solve the industry challenge of ad fraud. However, it does provide a solution whereby advertisers can be confident that their ads will appear on the sites they have selected.

Ad formats: Ads.txt does not specify every ad format that an authorized SSP is allowed to sell.

Using Ads.txt for campaigns

Smadex fully supports Ads.txt programmatic trading for mobile site buys. This is enabled at line level at zero additional cost from Smadex, unless advertisers specify otherwise.