Programmatic Advertising: What Are the REAL Challenges of SPO?

By Max Legrand · GreyFox Ads · A French perspective on programmatic advertising

When people talk about Supply Path Optimisation (SPO), the message is usually the same: “Find the best path to access inventory.” Except that… that is only half the story. 😉

SPO is about more than finding the shortest route

Supply Path Optimisation is often described as the process of choosing efficient routes between advertisers and publisher inventory. That matters: programmatic supply chains can contain several technical and commercial intermediaries.

But before comparing fees, there is a more fundamental question. Are two routes genuinely selling the same advertising opportunity? If they are not, a simple CPM comparison can be misleading.

Question 1: What am I REALLY buying on the publisher’s website?

This is, in my view, the most important SPO question. The Open Web contains excellent advertising opportunities — and some placements designed to exploit the signals DSP algorithms use to optimise campaigns.

• Small rendering: the creative is displayed at a much smaller size than a buyer may expect, limiting its share of screen.
• Fat-finger clicks: placements can generate very high click-through rates but poor landing-page engagement (for example, 10% CTR alongside 95% bounce rate — an illustrative warning sign, not a universal benchmark).
• Sticky small players: a small ad unit follows the user around the screen and may deliver impressive viewability at a low CPM, without necessarily delivering meaningful attention.

These practices can make a placement look attractive in a DSP dashboard while providing a much less convincing experience for the advertiser.

For more on these issues, read our analysis of small creative rendering and why viewability alone is not enough.

Same site, format and device — but very different results?

Imagine comparing two supply sources for the same site × format × device combination. One is the publisher’s own SSP seat; the other is a reseller’s SSP seat. If their performance differs dramatically, it is worth investigating whether they expose different placements or ad behaviours.

That difference is a reason to audit, not proof of wrongdoing: placement IDs, auction configuration, user mix, creative rendering and measurement differences may all matter.

To lift the veil on placements with suspiciously attractive performance, see our media-buying audit guide, and our practical article on auditing programmatic media buying.

Question 2: Am I buying the right placement through the most cost-effective path?

Once you have identified the placements you actually want, the classic SPO question becomes useful. The same publisher ad-server placement may be accessible through several routes:

1. A direct DSP-to-publisher connection, where available.
2. An SSP seat operated by the publisher.
3. An SSP seat operated by a reseller.
4. A more complex route involving a reseller connected to another reseller’s wrapper.

Additional intermediaries can add fees and complexity. But fewer intermediaries do not automatically mean better performance: the comparison must account for the actual placement, inventory access, services provided, auction dynamics and total cost.

For related reading, see our articles on reseller bid requests, Bid Repeating and value sharing in programmatic.

A practical two-step SPO checklist for Media Traders

Start with the advertising experience. Then optimise the path. Doing those steps in reverse risks optimising the cost of inventory you never wanted to buy in the first place.

How GreyFox Ads addresses both SPO challenges

At GreyFox Ads, our approach to the quality French Open Web starts by filtering supply to exclude placements and practices that undermine genuine advertiser effectiveness. We then select efficient SSP seats for quality publishers to avoid unnecessary intermediary costs.

That two-stage approach is part of our programmatic Master Deals: one curated deal designed to make activation simpler for Media Traders, with attention to inventory quality and transparent supply paths.

We also provide curation consultancy for programmatic sales houses and trading desks.

Original LinkedIn post: Read the original GreyFox Ads post.