Conversions API (CAPI).

An advertising pixel is a script in the browser that sends events to the platform. That works as long as the browser cooperates. Ad blockers, anti-tracking features, rejected cookies or interrupted page loads mean that some events never arrive. A Conversions API works one level lower: once your own server has stored an enquiry or booked an order, it reports that event directly to the platform. The event is then confirmed, not merely assumed.

The principle became known through Meta's Conversions API (Facebook and Instagram), often shortened to CAPI. Other platforms now have their own interfaces, including LinkedIn and OpenAI for ChatGPT Ads. At Google, Enhanced Conversions and offline conversion import play a similar role. What they all share is that hashed customer data such as email or phone number, technical details such as IP address and user agent, and click identifiers are sent with the event so the platform can attribute it to an ad contact.

Because pixel and API usually run in parallel, deduplication is crucial. Both routes send the same event with the same event ID. The platform recognises the duplicate and counts the conversion only once. If the shared ID is missing or differs, conversions are counted twice and the reports show better performance than was actually achieved. This check belongs in every setup and after every change to forms.

In data protection terms, server transmission does not change the basic rules. Hashed data is still personal data; passing it to an advertising platform needs a sound basis and must be described in the privacy policy, including transfers abroad. The advantage is control: the server defines exactly which fields are sent, and nothing is passed on unnoticed. The API is often connected via server-side tagging or directly in the backend.