What Is the Conversion API (CAPI)?
The Conversion API (CAPI) refers to a tracking interface that transmits conversion events (purchases, leads, sign-ups) directly from the advertiser’s server to an advertising platform’s servers, without going through the user’s browser. Popularized by Meta and later adopted by TikTok, Snapchat, and Pinterest, the Conversion API represents ad networks’ response to the disappearance of third-party cookies and to ad blockers that degrade traditional pixel-based tracking.
How Does the Conversion API (CAPI) Work?
The Conversion API relies on server-to-server communication. When a conversion occurs on the site, for example a validated order, the advertiser’s server sends a request directly to the advertising platform’s API, containing the event details: amount, transaction ID, timestamp.
To attribute this conversion to an ad exposure, the request includes matching parameters: click identifier (such as Meta’s fbclid), hashed email or phone number, IP address. The platform matches these signals against its user base to reconstruct the original ad journey.
The Conversion API is generally deployed alongside the pixel, with a deduplication mechanism based on a shared event identifier: if the pixel and the CAPI both report the same conversion, the platform counts it only once.
Why Is the Conversion API (CAPI) Important in Marketing?
Browser tracking is becoming less reliable: ad blockers, Apple’s restrictions (ITP, App Tracking Transparency), refused consent, and the disappearance of third-party cookies cause advertisers to lose a significant share of their measured conversions. The Conversion API restores this visibility by bypassing the browser, which improves both reporting and the performance of bidding algorithms, fed by more complete signals.
The stakes are directly financial: more comprehensive measurement makes it possible to reallocate budgets toward the channels that actually perform. TrackAd clients who strengthen their data collection see an average of +21% ROI gained within 2 months. Conversely, a poorly deduplicated CAPI artificially inflates conversions and distorts decision-making.
The Conversion API (CAPI) at TrackAd
TrackAd integrates data streams from the Conversion API into its data reconciliation layer: conversions reported server-side by each ad network are checked against actual transactions from the e-commerce back office, in order to detect duplicates, discrepancies, and conversions claimed by multiple platforms. This collection process is industrialized for TrackAd’s 150+ clients in France and internationally, with 100% of useful data collected and automatically updated every day.
Frequently Asked Questions
What’s the difference between the Conversion API and the conversion pixel?
The conversion pixel runs in the user’s browser and can be blocked by ad blockers or cookie restrictions. The Conversion API transmits the same events from the advertiser’s server, in a more reliable and controlled way. The two are complementary: most advertisers use them together with a deduplication system.
Does the Conversion API work without cookies?
Yes, that’s precisely its value. The Conversion API doesn’t depend on third-party cookies: it relies on matching parameters like the click identifier or hashed customer data (email, phone number). Attribution remains more accurate, however, when first-party identifiers are available and included in the request.
How do you set up a Conversion API?
Three main approaches: native integration via the CMS or e-commerce platform (Shopify, PrestaShop), deployment via Google Tag Manager server-side, or direct development on the ad network’s API. In all cases, deduplication with the existing pixel must be configured, and event matching quality must be verified.
Is the Conversion API GDPR compliant?
The Conversion API doesn’t exempt you from consent requirements: transmitting personal data (even hashed) to an advertising platform remains subject to GDPR and CNIL rules. Server-side tracking does, however, give the advertiser better control over the data sent, which makes it easier to filter based on consent status.
How many additional conversions can CAPI help recover?
This varies depending on the audience and device: advertisers generally see an improvement in conversion coverage of around 10 to 30% compared to the pixel alone, particularly on restrictive browsers like Safari. The exact gain is measured by comparing deduplicated conversions before and after deployment.
The Conversion API (CAPI) is a server-to-server tracking channel that transmits conversions directly from the advertiser’s server to advertising platforms, without depending on the browser or third-party cookies. It strengthens the measurement and optimization of campaigns, provided it’s properly deduplicated and reconciled with actual sales.