Focused on the areas of data, cost and inventory source, the guide provides questions for each stakeholder category to be asked at various stages of the digital advertising supply chain.

The guidance has been developed by IAB Europe’s newly formed transparency working group, which brings together members of the brand advertising and programmatic trading committees to coordinate industry initiatives to enhance transparency.

Transparency is seen as a barrier to investment in programmatic advertising by 40% of advertisers, according to an IAB Europe survey.

Simon Halstead, chair of IAB Europe’s programmatic trading committee and head of open demand international at Oath, said the guide allows partners to identify "the right questions" in the area of transparency. He added: "As the industry evolves with initiatives like IAB led Ads.txt and the impact of GDPR, all parties need to engage in detailed conversation to drive transparency.”

Daniel Secareanu, board director of IAB Europe and chief digital officer, Burda Romani, said: “In order for the programmatic trading ecosystem to continue to grow and provide added value to the industry and its stakeholders we need to make sure that everyone has a clear image of how this ecosystem works. We can only do this by ensuring that the programmatic trading currency (inventory and data) and its supply chain are fully transparent to everyone involved in it.”