The Meta Pixel sends an event from the visitor's browser. The Conversions API sends an event from your server. When both report the same purchase, Meta needs a way to tell that they are one purchase, not two. This article covers that pairing: what the server event contains, how deduplication decides what counts, how customer data must be prepared, and how to check the result before trusting the numbers.
One purchase, two events
A server event is a POST request to https://graph.facebook.com/{API_VERSION}/{PIXEL_ID}/events with an access token, as described in Using the Conversions API. The example on that page used version v27.0 when this was written. The request body holds a data array with up to 1,000 events.
According to the server event parameters reference, four fields are required for every event: event_name, event_time, user_data and action_source. For website events, event_source_url is also required. event_id is marked optional, but Meta recommends it for deduplication.
Two timing rules matter here. event_time is a Unix timestamp in seconds, and it can be at most 7 days before the moment you send it. If any event in a request is older than that, Meta returns an error for the whole request. Meta also recommends sending events as soon as they occur, ideally within an hour.
