ChatGPT ads: OpenAI's pixel starts with consent switched on, and what it changes for your measurement
Alexandre Suon·10 min read·
ChatGPT ads reached France and 30 other European markets in August. The pixel that measures their conversions assumes the visitor said yes, unless the site tells it no. What this pixel is, what the documentation says, and how to check your numbers are clean before you present an ROI.
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30-second summary
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- Since August 2026, ChatGPT ads have been available in 31 European markets, including France, for users on the Free and Go plans.
- To measure conversions, OpenAI provides a pixel that advertisers install on their site.
- Its documentation says it plainly: the pixel initializes consent to “true” by default, unless the site sets it to “false” or the pixel finds a stored denial.
- Didomi, a consent banner vendor, reminds advertisers that consent handling is their responsibility, and publishes a how-to.
- A badly wired pixel creates legal risk and skews measurement: test the refusal path before any launch.
Section 1 · The news
ChatGPT ads have reached Europe, with their own measurement pixel
On August 18, 2026, OpenAI announced ChatGPT ads in 31 European markets, including France, Germany, Spain and Italy. They only show to users on the free plans (Free and Go), always labeled and separate from answers. Since August 31, advertisers can run campaigns themselves in Ads Manager.
To know whether an ad drove a sale, OpenAI offers several measurement tools, including a pixel installed on the site and a server-side Conversions API. It is the pixel's default setting that raises the question.
What is a pixel? A small script placed on the site's pages. When a visitor who came from an ad takes an action (views a product, adds to cart, orders), the pixel sends a signal to the ad platform. That is what lets you say “this campaign drove 40 orders”.
Section 2 · The default
Without a contrary signal, the pixel assumes the visitor said yes
OpenAI's developer documentation is explicit: the pixel “initializes consent to true by default unless you set it to false or the Pixel finds a stored denial.” In other words, if the site tells it nothing, it measures.
- 1No signal from the siteConsent is treated as granted. Conversion events are sent.
- 2The site sets consent to “false”The pixel stops sending measurement events, and its two cookies are removed.
- 3The visitor then acceptsThe site sets consent back to “true”. Later events are sent; events blocked earlier are not replayed.
The documentation also lists the data used: an attribution identifier taken from the landing page URL and a randomly generated browser reference, stored in two first-party cookies. OpenAI says it does not currently use this data for user-level personalization.
Why the default matters Many tools wait for a “yes” before starting. This one waits for a “no” to stop. If the consent banner is not wired to the pixel, nothing stops it from measuring visitors who declined.
Section 3 · The rules
Consent remains the advertiser's responsibility
In Europe, setting a cookie or reading information on a visitor's device for ad measurement generally requires their prior agreement. That is the job of the consent banner and the platform behind it, the CMP.
In its October 14, 2026 article, Didomi, a CMP vendor and Henkan partner, puts it in one sentence: consent handling is the advertiser's responsibility. OpenAI does not decide whether your pixel runs; your site does.
CMP: what are we talking about? Consent Management Platform. The tool that shows the banner, records each visitor's choice, and passes it to the site's tags so they fire, or don't.
Section 4 · The wiring
Two ways to wire the pixel to consent
Didomi describes two options, depending on how the pixel is installed. Either way, OpenAI must first be declared as a vendor in the banner, linked to a consent-based purpose such as “measure advertising performance”.
| Installation | What you do | Result |
|---|---|---|
| Through a tag manager | The pixel tag only fires once the visitor has accepted OpenAI | The pixel never loads before consent |
| Directly in the code | Set consent to “false” before initialization, then to “true” after the visitor agrees | The pixel loads but sends nothing without consent |
Didomi also notes that a pixel runs in the browser: ad blockers and browser restrictions can stop some conversions from being reported. OpenAI's Conversions API can send the same events from the server, as a complement.
Section 5 · Measurement
A badly wired pixel inflates your conversions, then makes them drop
The legal risk is the visible one. The measurement risk is sneakier. If the pixel also counts visitors who declined, conversions attributed to ChatGPT are inflated compared with other channels, which do respect the refusal.
- Cross-channel comparison is skewed: ChatGPT looks more profitable than Google or Meta simply because it counts more people.
- The day it is fixed, numbers drop at once, with no change in real performance.
- The ROI shown to leadership becomes fragile, and so does trust in the numbers.
“An inflated number costs more than a low one: decisions get made on it.”
Section 6 · What to check
Test the refusal path before the first campaign goes live
The check takes about ten minutes. Didomi describes it in its how-to, and it is the one we recommend before any new pixel:
- Open the site in a private window and decline the banner.
- Browse and simulate a conversion, then check in the Ads Manager Conversions tab that no event arrived.
- Repeat while accepting, and check that events do come through.
- Log the test date and run it again after any change to the banner or the tag manager.
- Compare volumes with other channels during the first weeks to catch anomalies.
Key terms
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- Pixel
- A script on the site that tells an ad platform what visitors from its ads do, to measure conversions.
- Consent
- The visitor's prior agreement, collected by the banner, to set cookies or track their activity for advertising.
- CMP
- Consent Management Platform: the tool that shows the banner, records choices and passes them to the site's tags.
- Tag manager
- A tool (Google Tag Manager, for example) that decides when each script on the site fires.
- Conversions API
- Sending conversions from the site's server rather than the browser, less affected by blockers.
- Attribution
- The rule that links a sale to the ad that triggered it.
Sources
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Alexandre co-founded and runs Henkan & Partners. He decodes one e-commerce story every day on LinkedIn.
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