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HTTP Method: POST URL: /api/v3/events/{eventId}/registrants Authentication: Requires API Key in the request header. Path Parameters:
ParameterTypeDescription
eventIdstringID of the event to register the audience to. To find this value, visit the schedule page and click “Copy event ID” in the three dots menu.
Request Body Paramaters:
  • email: Email address of the registrant. Must be unique per event.
  • first_name: Registrant’s first name.
  • last_name: Registrant’s last name.
  • custom_fields: Key-value map of custom registration fields. Keys are custom field names, values are the submitted responses.
    Notes:
    • email, first_name & last_name are always mandatory for every webinar.
    • Rest of paramaters are mandaroty only if defined so in the registration form setup when scheduling the event.
    • phonefield: phone number in international format, seperated to country code and phone number.
    • text field limited to 256 charachters.
    • checkboxfield: limited to TRUE or FALSE
Response: confirmation for registration, including the event ID and unique join URL. Rate limit: once every 10 seconds for unique request. Status Codes:
  • 200 OK Registration created successfully. 401 Unauthorized Authentication failed (Invalid or missing API token).
  • 404 Not Found Event not found.
  • 409 Conflict Duplicate registration (a registrant with the same email already exists for this event).
  • 422 Unprocessable EntityValidation error (for example, invalid email format, unsupported country code, or invalid custom_fields payload).

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Sample Request

POST /api/v1/events/123/registrants HTTP/1.1
Host: platform.riverside.fm
Authorization: BEARER YOUR_API_KEY

{
  "email": "[email protected]",
  "first_name": "Ada",
  "last_name": "Lovelace",
  "custom_fields":  [
	{
      "label": "how many webinars did you attend?",
      "value": "one"
    },
    {
      "label": "Country",
      "value": "United States"
    },
    {
      "label": "Phone",
      "value": {"countryCode":"+1","phoneNumber":"555555555"}
    },
    {
      "label": "Do you agree to be contacted?",
      "value": true
    },
    {
      "label": "Question",
      "value": "Answer 1"
    }
  ]
}

​
Sample Response

{
  "event_id": "ev_456",
  "join_url": "https://riverside.fm/webinar/ev_456?token=abc123..."
}

​
Error Responses

Duplicate Registration (409) 
{
  "statusCode": 409,
  "message": "Email already registered for this event"
}
Validation Error (422) 
{
  "statusCode": 422,
  "message": "Validation failed",
  "errors": [
    {
      "field": "email",
      "message": "Invalid email format"
    }
  ]
}
Event Not Found (404) 
{
  "statusCode": 404,
  "message": "Event not found"
}