Conversions API (CAPI)
A Conversions API (CAPI) is a server-side interface that sends conversion and event data directly from a business's servers to an ad platform, rather than relying solely on a browser pixel. It exists because in-browser tags increasingly miss events due to tracking prevention, ad blockers, and lost cookies; a server connection can pass events the browser never reported, subject to consent and matching.
What this means
Browser pixels fire from the user's page and depend on the browser allowing cookies, scripts, and network calls to the ad platform. Tracking-prevention features, extensions, and consent choices mean a growing share of conversions never reach the platform that way.
A Conversions API moves the reporting to the server: your backend sends a structured event (purchase, lead, sign-up) directly to the platform's API, with hashed match keys and event metadata. This can recover events the browser dropped and reduces dependence on third-party cookies, though it does not bypass consent.
Matching, dedup, and consent
Because the same conversion may arrive from both the pixel and the server, platforms deduplicate using a shared event ID so it is counted once. Matching back to an ad interaction relies on hashed identifiers (email, phone) and contextual signals the user provided — not on covert fingerprinting.
Consent and data-minimization rules still apply: a server channel does not create a legal basis. Meta's Conversions API and Google's equivalents document required event fields, hashing, and deduplication. Treat CAPI as a signal-quality improvement that must be deployed within your consent framework.
- Server-to-server event delivery, independent of browser blocking
- Deduplicated against the pixel via a shared event ID
- Consent and hashing requirements still apply
How it appears in analytics and logs
If platform-reported conversions rise after enabling CAPI without more real sales, you are recovering previously-lost browser events, not generating new conversions.
Diagnostic use case
Send conversions via a Conversions API to recover events that browser pixels miss, improving the completeness of the data an ad platform attributes and optimizes on.
What WebmasterID can help detect
WebmasterID records conversions first-party and server-side-classified, which is the kind of clean event source a Conversions API integration relies on.
Common mistakes
- Assuming server-side sending removes consent obligations.
- Forgetting to deduplicate pixel and server events with an event ID.
- Reading recovered events as net-new conversions.
Privacy and accuracy notes
CAPI still requires a lawful basis and user consent; sending events server-side does not remove consent obligations. This page is educational, not legal advice.
Related pages
- Server-to-server conversion tracking
Server-to-server (S2S) conversion tracking reports a conversion from one server directly to another — typically your backend to an ad platform or affiliate network — keyed by a click ID captured at the landing visit. It removes the dependence on a browser pixel firing at conversion time, which matters for offline conversions, multi-step flows, and environments where client tags are unreliable.
- Server-side attribution and tagging
Server-side attribution moves the collection and forwarding of measurement events from the browser to a server you control — via server-side tag management or platform conversion APIs like Meta's CAPI. It can improve resilience to browser restrictions and give you governance over what data leaves your environment, but it is a data-flow change, not a way to bypass consent.
- Enhanced conversions
Enhanced conversions is a Google Ads feature that supplements cookie-based conversion measurement by sending hashed first-party customer data — such as an email address the user provided — to match conversions that cookies alone would miss. The data is hashed (SHA-256) before transmission. It is one industry response to the decline of third-party identifiers, with its own consent and configuration requirements.
- Privacy-first analytics
Capture conversions first-party with consent in mind.
Sources and verification notes
- Meta for Developers — Conversions APIDocuments server-side event delivery, deduplication, and matching.
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.