What Is the Meta Conversions API (CAPI)?
The Meta Conversions API (CAPI) is Meta's server-to-server interface for sending conversion events from a website, app, CRM, or offline source directly to Meta rather than through the browser Pixel.
Each event names an action_source describing where it happened and carries matchable user parameters, which are hashed before transmission. When a server event duplicates a Pixel event, Meta uses event_name plus event_id to recognize the pair and count the action once.
- Match parameters
- email addressphone number
- deduplication with the Pixel
- event_nameevent_id
Daniil Maximkin Published Reviewed
- In practice
How does the Conversions API work?
The Conversions API sends events from a server, backend, or CRM to Meta over HTTP, so actions the Pixel never observed — an off-site purchase, a phone call, a CRM order — can still reach Meta and land in the same dataset.
Each event carries an event name, a time, and a set of parameters; website events also require the source URL and the client user agent, the browser context Meta cannot see.
- In practice
What is action_source for?
action_source states where the conversion happened, and Meta requires it on every event sent through the API. Sending it accurately is a condition of using the API.
The accepted values cover how a conversion can occur: website, app, phone call, chat, physical store, email, system-generated, business messaging, and other. A wrong source misrepresents where the conversion came from.
- In practice
What are hashed user parameters?
Match parameters are the customer identifiers that let Meta connect a server event to a real account, such as an email address or phone number. Personally identifiable values must be hashed before they are sent, which the Business SDK does automatically.
Sending several independent match parameters gives Meta more ways to confirm the event belongs to a real person, which is what Event Match Quality measures.
- In practice
How does deduplication with the Pixel work?
Meta pairs a browser event with its server copy using event_name and event_id. The Pixel sends the value as eventID and the Conversions API as event_id; the two must be the same string to be recognized as one action.
If the identifiers differ, Meta may count the browser and server events separately, which overstates conversions. If they match, the action is counted once.
- Not to be confused with
Not to be confused with Is not Is a replacement for the Pixel Meta's server-to-server interface The Conversions API is not a replacement for the Pixel, and it does not bypass consent or browser privacy protections. The recommended setup sends the same events through both channels and deduplicates them, because each observes things the other misses.
A server event is not automatically more accurate: its match quality depends on the identifiers it carries.
- Where to check
How do I verify server events in Events Manager?
- Meta Events ManagerdatasetOverview
- Meta Events ManagerdatasetTest Events
Open Meta Events Manager and select the dataset. The Overview shows which event sources are reporting, and the Test Events tool shows an incoming event’s parameters, including whether it arrived from the server and whether it was deduplicated against the browser.
The diagnostics surface events that arrive without a shared identifier, the fastest signal that the event_id pair is missing.
