Media Traders: How Can You Audit Your Own Programmatic Media Buying? 🕵️

By Max Legrand · GreyFox Ads · Programmatic buying guide

One thing media traders sometimes underestimate about their programmatic campaigns (partly because major DSPs do not always provide the transparency we would like) is that, above all, they are buying placement IDs.

1. Why are placement IDs so important in programmatic advertising?

You can buy inventory on the same website, on the same device, in the same format—and still see enormous differences in performance between campaigns. Why? Because the individual placement can change the whole experience.

One placement may put your creative in a prominent position. Another may squeeze it into a tiny sticky unit. Both can appear in a report under the same publisher and format.

That's why we keep coming back to placement IDs as a key optimisation dimension and to the problem of small rendering.

So here's a question for media traders: instead of looking only at the statistics at the end of the campaign, why not check what we're actually buying in the Open Auction?

2. Which dimensions should you include in a DSP media-buying audit?

Start by pulling a report of your purchases. At a minimum, ask for these dimensions:

If your DSP does not expose some of these dimensions in its interface, call your account manager and ask for the underlying reporting data (availability and granularity vary by platform).

Focus your investigation on combinations of site × device × format × placement ID, keeping the exchange and SSP seat alongside them so that you can understand the supply path.

3. How can you inspect a programmatic placement yourself? A five-step DSP audit

Here's the hands-on approach from our original guide, with one important condition: run the experiment only on an account and device you control, using an authorised test setup and the consent required for any tracking.

1. Create a test audience. In your DSP, configure a permitted retargeting pixel or segment for your own browser/device.
2. Prepare the test tag. Export the pixel tag into a text editor and save it as an .html file, if this is a supported and authorised implementation for your DSP.
3. Load the tag. Open the test file in Chrome on the device you want to audit (the pixel must actually fire and the DSP must be able to recognise the test audience).
4. Set up a tightly scoped test line item. Our illustrative setup used a €5 budget and a €50 CPM bid, restricted to the retargeting audience and the relevant site, device, format and placement ID. If placement-ID targeting is not available in the interface, ask your DSP account manager whether the API supports it.
5. Visit the publisher's site. Browse on the relevant device, make the applicable consent choice and look for your creative in the placement you selected. If it serves, inspect its actual rendering on screen.

There you have it: a chance to lift the lid on the placement IDs behind the numbers. 🔎

4. What are the limitations of a €5 DSP placement test?

A high CPM bid does not guarantee that your creative will appear. Audience minimums, auction competition, consent signals, browser restrictions, deal eligibility, publisher rules, creative approval and DSP policies can all prevent delivery.

Some DSPs also restrict retargeting audiences or targeting at the individual-user level. If the setup is not permitted or technically supported, do not work around those restrictions; use a publisher-provided placement preview, an approved QA environment or a direct placement audit instead.

And a visible test impression is a useful observation, not proof that every impression bought on that placement will render identically. Test across relevant pages, devices and conditions.

5. Which placements deserve a closer look?

Start with the ones reporting extraordinary results: CTRs above 10%, suspiciously cheap clicks, or video completion and viewability figures that look almost too good to be true. 😉

These numbers do not prove fraud on their own. But they should prompt you to examine creative size, actual screen share, sticky positioning, accidental-click risk and the quality of the supply path.

For related reading, see our articles on the limits of viewability optimisation, attention on the Open Web and reseller-heavy supply chains.

6. How does GreyFox Ads approach programmatic inventory quality?

At GreyFox Ads, we will struggle to promise clicks at €0.04 or viewable CPCVs below €0.01. Why? Because we deliberately exclude certain types of placements that can make those headline metrics look impressive without necessarily delivering real effectiveness.

• 🚫 Ad-cluttered websites and subdomains: avoid the so-called “Christmas tree” effect.
• 🚫 Tiny screen-share placements: prioritise the actual impact of the creative rather than the nominal format alone.
• 🚫 Unnecessary reseller SSP seats: favour direct publisher seats and reduce avoidable intermediary fees.

We believe the French Open Web deserves more than a race to the cheapest possible KPI. What matters is real advertising effectiveness—and understanding exactly where the ad appears is a good place to start.

Learn more about our Master Curated Deal and programmatic curation.