IAB Tech Lab Launches ‘id-sources.json’ Proposal for Post-Cookie World

13 October, 2021 

IAB Tech Lab, an industry standards-setting body, has today released ‘id-sources.json’, a technical specification designed to create transparency around ID solution usage. The new standard has been born out of the Rearc Accountability Working Group, Tech Lab’s hub for developing post-cookie solutions.

The idea behind id-sources.json is to enable companies to easily and transparently declare which identity sources they use to other companies in the digital ad supply chain. In the post-cookie world, it’s likely we’ll see publishers, advertisers, and ad tech companies working with a range of different identifiers. To navigate this complexity, it will be important for companies to be able to keep track of which solutions that partners are using.

Tech Lab says that by enabling this, id-sources.json should have wide reaching benefits for all players. Brand and agencies for example should be able to map out which publishers work with which identifiers. They can then map that against their own audiences, which will themselves be associated with different identifiers. This will help them figure out where in the publishing landscape they can locate their addressable audiences.

“As companies turn to different identity solutions that will replace the role of the third-party cookie, it’s important we continue to push for a transparent supply chain,” said Caitlin Fitzharris, senior product manager at Index Exchange. “Knowing which identifier is used by whom helps all parties, and id-sources.json is an important step towards building auditable data structures to ensure consumer privacy.”

A familiar format

Readers familiar with the works of IAB Tech Lab will notice a running theme – this is the third specification it’s released which uses ‘.json’ files, following sellers.json and buyers.json.

Both of those specifications are similarly designed to increase transparency in the advertising supply chain, by enabling sellers, buyers, and ad tech middlemen to easily declare which ad tech companies they trade through.

This new specification is designed to work similarly. Publishers list the identifiers they’re working with in a publicly viewable .json file (which is just a specific type of file). These can be viewed via a subdomain of that publisher’s website.

That then allows software to crawl publisher sites, access those files, and record the relevant information. Overall, this should ease ad campaign execution between advertisers, publishers, and their chosen technology providers.

The idea is fairly simple, but that’s the point. As with sellers.json, buyers.json, and ads.txt before, Tech Lab hopes that by making its standards easy to implement, adoption will be high – which is crucial to their success.

Accelerating consolidation?

New standards don’t tend to be headline grabbers – but they can have a big impact. What will be particularly interesting to see is whether id-sources.json has any influence in driving consolidation around a smaller number of identifiers.

There’s been a lot of speculation that in the post-cookie world, we’ll see most participants in the ad tech supply chain group around a small number of identifiers. But in the build up to the cookie-pocalypse, some have chosen to wait to see which identifiers pick up mainstream adoption, before committing to any in particular.

By laying out exactly which identifiers are used by which publishers, id-sources.json could help introduce more clarity around which identifiers are proving most popular, thus accelerating that consolidation.


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