What is principal media?

So, what exactly is Principal Media?

Principal media, sometimes called inventory media, is where advertising agencies take a more direct role in media buying. Instead of acting purely as intermediaries for their clients, agencies purchase media inventory upfront from publishers. They then resell it to their clients, adding a markup.

It’s like a wholesaler with a velvet rope. Agencies claim ownership over the media inventory and become, in a way, their own media platforms.

Mega Glossary of Digital Advertising Terms

I’ve compiled over 150 essential advertising terms into what I’m affectionately calling the Mega Glossary. Not just dictionary definitions, but real-world explanations of what these terms actually mean in practice. MMM variables? Got ’em. That mysterious “Performance Max” your Google rep keeps pushing? Covered. Privacy Sandbox? Unfortunately, yes – we need

ADLINGOTravis Lusk

In this model, agencies act not as agents working on behalf of their clients but as owners—or “principals”—of the inventory.

What this means for clients is a bit of a shift. On one hand, they’re accessing media inventory that the agency has already locked in, often at a discount. On the other, they’re stepping into a market where challenges like transparency, trust, and cost-effectiveness all come into play.

WTF is principal media?

The use of principal media is on the rise, notably by the agency holding companies, which are looking for profit wherever they can find it. But how do clients feel about it?

DigidayMichael Bürgi

Why it's not just business as usual

Let’s lay out the stakes.