ads.txt – What is ads.txt? How to implement for AdSense and others

September 2017

What is ads.txt?

Ads.txt, also known as Authorised Digital Sellers, is the IAB Tech Lab’s initiative to clean up and bring transparency to digital advertising by eliminating the ability to profit from counterfeit inventory. This is achieved by providing a mechanism to publishers so that they can declare who is authorized to sell their inventory.

Although this has had an almost immediate impact on publishers, including those just using AdSense, many publishers are still unaware of it. The initiative came about in the wake of a number of scandals around the misrepresentation of ad inventory that resulted in big money being spent on bad inventory.

The solution, backed by the IAB and most of the big players in the ad space is deceptively simple (and for once cheap and easy for publishers of all sizes to implement).

Shortly after ads.txt was introduced in 2017, Google announced that they would no longer be buying inventory from sites that have an ads.txt file that doesn’t match the ad request, making it imperative that publishers have their ads.txt correctly set-up right away if they have the file present.

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How does ads.txt work?

Authorised Digital Sellers is simply a text file that sits on your server and lists the places that are authorised to sell ads on your behalf. The idea is simple: Buyers can collect this data and be sure that if they’re paying for ads on rollingstone.com then that is where those ads will appear (see example from rollingstone.com/ads.txt).

Effectively, it is a file that publishers can add to their site to certify their ownership of the site and list the accounts that are authorised to sell their inventory, doing so in a format that can be easily crawled and indexed.

What do publishers stand to gain from implementing ads.txt?

Ads.txt is beneficial to both publishers and advertisers. If you are the New York Times, the benefit is obvious: Advertisers looking for exposure on your site won’t be tricked into buying misrepresented inventory and you retain control overpricing. As the standard gains more widespread adoption, buyers are more likely to require ads.txt for all buys, making it more relevant to less well-known publishers too.

What are the drawbacks of implementing ads.txt?

The initiative is not without some criticism. Ads.txt is designed to bring transparency, but some argue that it is too transparent. Implementing ads.txt shows exactly where you sell your inventory to anyone who cares to look.

If you price your ad inventory differently through different channels this allows buyers to shop around for the lowest price. Take, as an example, the ads.txt file for Business Insider :

#Ads.txt uk.businessinsider.com

google.com, pub-1037373295371110, DIRECT #video, banner, native, app
rubiconproject.com, 10306, DIRECT #banner
indexexchange.com, 183963, DIRECT #banner
indexexchange.com, 184913, DIRECT #banner
openx.com, 537147789, DIRECT #banner
openx.com, 538986829, DIRECT #banner
appnexus.com, 7161, DIRECT #banner
appnexus.com, 3364, RESELLER #native
facebook.com, 1325898517502065, DIRECT #video, banner, app
liveintent.com, 87, DIRECT #banner
taboola.com, 688168, DIRECT #native
triplelift.com, 4139, DIRECT #native
teads.com, 11643, DIRECT #outstream
teads.com, 11445, DIRECT #outstream
google.com, pub-8415620659137418, RESELLER #native

If I’m buying ads on Business Insider through one of these partners I can easily see where else inventory is available. I even have the relevant account IDs should I care to go comparing prices.

Business Insider have even gone one step further and kindly labelled each demand partner with the types of ads they serve, although this is not part of the standard. Again, these are “big publisher problems” that many independents would like to face, but they are also important to be aware of.

Should publishers adopt ads.txt?

Compared with other initiatives publishers are encouraged to adopt, the implementation cost of ads.txt is incredibly low and just five minutes work is enough to get most sites compliant. According to BuiltWith, 30% of the top 10,000 websites currently use ads.txt with adoption being lead by the USA, Russia and the UK.

The low cost and ease of adoption means that this could suit independent publishers who aren’t concerned about the transparency issue and have the flexibility to rule out change more easily.

Implementing ads.txt for Google AdSense and Google Ad Manager

Implementing ads.txt is incredibly simple. Create a text file and add one line per authorised partner. On each line add the following three pieces of information, separated by a comma:

The domain of the advertising system
Your account ID
The type of relationship you have with that partner (either DIRECT or RESELLER if you are working through a third party)

There is an optional 4th field which is the TAG ID of the source if they are certified by the Trustworthy Accountability Group. Once created simply upload that file to your webserver so that it is visible at example.com/ads.txt and you are done.

Google are pushing hard on ads.txt . Whilst they haven’t said that they will stop bidding on inventory that doesn’t have a corresponding ads.txt file, they will stop buying and selling unauthorised inventory in Q4 2017.

In practice, that means that there is more immediate risk to AdSense and Ad Exchange publishers from badly implementing ads.txt than not implementing it. This makes it doubly important to ensure that:

If you use an ads.txt file you must include declarations for an AdSense and Ad Exchange accounts that you serve
Those declarations need to be correct

Authorised Digital Sellers for AdSense

If you publish ads via Google AdSense and want to implement ads.txt you will need to first locate your publisher ID. This can be found by logging in to AdSense and then navigating to Settings > Account > Account information.

Your publisher ID is in the format of pub-0000000000000000 with the zeros replaced by your own 16 digit number.

The entry in ads.txt for a publisher’s own Google AdSense account will then look like:

google.com, pub-0000000000000000, DIRECT, f08c47fec0942fa0

Please note that the TAGID for Google is always f08c47fec0942fa0 . Also, don’t forget to include the pub- part of your publisher ID, as this is apparently one of the most common errors in ads.txt implementation for AdSense publishers.

Many AdSense publishers see warnings in their account regarding ads.txt . The warning states:

Earnings at risk – One or more of your ads.txt files doesn’t contain your AdSense publisher ID. Fix this issue now to avoid severe impact to your revenue.

ads.txt warning

This in-account warning complements notices that are being sent by email in the following format:

Dear Publisher,
We’ve noticed that the ads.txt file on one or more of your sites that you monetise through this AdSense account (pub-xxxxxxxxxxxxxxxx) is missing the correct publisher code.
From mid-October, Google will stop buying ads on sites with ads.txt files which don’t include the correct publisher IDs. We recommend you update your ads.txt files immediately to prevent impact to your earnings. Make sure that the ads.txt file for each site you want to monetise through this account contains the snippet below:
google.com, pub-xxxxxxxxxxxxxxxx, DIRECT, f08c47fec0942fa0
It may take up to 24 hours for AdSense to process your updated ads.txt files.
You can learn more about ads.txt, how buyers will use it and how to implement it on your sites in our Help Centre.

Authorised Digital Sellers for Google Ad Manager

The set-up for publishers with their own direct Google Ad Manager account is the same, with the ID being found through GAM by navigating to Admin > Global settings > All network settings. Again the Publisher ID is in the format of pub-0000000000000000.

For publishers accessing Ad Exchange through a GCPP (such as OKO) or another third party, the process is the same, but they will need to get the publisher ID from their managing partner and specify it as reseller.

To take the example of a publisher using their own AdSense account and accessing Ad Exchange through a partner, their ads.txt file will look like the example below (We’ve labelled with a #comment for clarity):