Eventarc delivers events, regardless of provider, to the target destination in a CloudEvents format using an HTTP request in binary content mode. CloudEvents is a specification for describing event metadata in a common way. Using a standard way to describe event metadata ensures consistency, accessibility, and portability.
Target destinations such as Cloud Functions, Cloud Run, and GKE consume events in the HTTP format. For Workflows destinations, the Workflows service converts the event to a JSON object, and passes the event into the workflow execution as a runtime argument.