Lately, I’ve been seeing a lot of LinkedIn posts debating who invented header bidding. So, as someone who’s been in AdTech for 17 years (yeah, I’ve seen it all—pre-RTB, pre-Google AdX, the Wild West days of ad-exchanges), let me give you my two cents on this heated topic.

Back in the day, Right Media Exchange (RMX) was the only true ad-exchange—anyone could buy, anyone could sell. Then came real-time bidding (RTB), and the first significant use-case? Retargeting.

Now, here’s where things get personal. My previous startup, Vizury, was one of the first companies to dive into retargeting (at least, in our minds, we were the first—Criteo wasn’t even on our radar at the time because we were focused on Asia). In 2007, we first set out to build a behavioral targeting ad-network, but quickly realized that the biggest challenge to building an ad-network wasn’t technical—it was operational (sales on both the buy and sell side? No, thanks!).

The Birth of Retargeting (Or How We Accidentally Stumbled Upon It)

One day, we started tracking “drop-off” users—people who visited the thank you page post conversion. We had our pixel on this page to track conversions. The next day, when we were analyzing the previous day’s data, we found a small pocket of uses where the CTR was super high (10x the average). When we dug in further, we realised that all these users were “drop-off” users. We then set out to understand how we can show ads only to these users & nobody else & we released that there is a way. Boom—drop-off targeting was born! This was a mind-blowing moment for us. We expanded this across different pages and started leveraging RMX’s pixel-based targeting.

Then RTB came along, fueling growth with Google AdX, Facebook Exchange, and the like. Around the same time, PubMatic and Rubicon pivoted from yield optimizers to SSPs. And guess who else showed up? Criteo.

Now, Criteo didn’t start as a retargeting company—they originally focused on product recommendations. But when they shifted gears to retargeting & shifted base to the US. As retargeting started gaining more traction & RTB became more prevalent, Criteo did something brilliant: going direct to premium publishers. Instead of waiting for inventory to hit the ad-exchange/ open-auctions, they put a tag on the publisher’s header, siphoned off high-value users through a direct line-item in Google Ad Manager (GAM), and snapped up inventory before it even hit price-priority or the open-auctions. Essentially, they were locking in the best users before anyone else had a chance to even bid on them.

And they didn’t just do this once. We saw this pattern repeat every time Criteo entered a new market. Their direct supply was likely much bigger than their open-market supply. Meanwhile, at Vizury, we had internal debates: should we focus on open-market supply or go direct to publishers? We convinced ourselves that all supply would eventually become open; even if not all inventory, certainly the ability to reach all users through open-auctions is inevitable, so there was no need to go direct. Hidden bias in this conclusion is also Vizury’s dislike towards anything that required a lot of operational work – certainly, going directly to publishers seemed a fairly tedious job. But, what a massive mistake. Google and Facebook became walled gardens, throttling supply, launching their own remarketing products. Eventually, turned out having direct access to supply through publisher integrations/partnerships was a game changer.

So, Who Really Invented Header Bidding?

If we’re being honest, it wasn’t any SSP or any AdTech guru—it was Criteo.

They were the first to place a tag in the header of a publisher’s page, mark users with a key-value, and extract inventory off GAM through a line-item targeted to the key-value. And if you think about it, that’s exactly how header bidding works.

So, case closed: Criteo was the OG of header bidding.

I’d love to hear your thoughts—do you agree, or are we still arguing about this in 2025?