API Message Format

The Helcim API consumes requests in JSON format with all required information in the request header and body, and returns a JSON object as a response.

When a successful connection is established to our API, a standard 200 HTTP status code will be returned for successful requests. You should not assume that a 200 status code indicates that the requested action was successfully performed; instead you should refer to the response object for more information on the outcome of the request.

Request Header

Only authorized users may call Helcim API endpoints. In order to authenticate with our service, send your API token in the header of your request and ensure that the permissions for your respective token allow for the request you are making.

Along with your API token, your request headers should include accept and 'content-type' parameters set to 'application/json'.

Example Header for Payment API request

Example Header for Payment API request

Request Body

Body parameters should be sent in your request in JSON format. Each respective endpoint has certain required body parameters to be sent in your request.

Review our API reference documentation to see what information is required for the endpoint that you are calling, or review the specific API documentation under Overview of the Helcim API for more detailed information about header and body fields.


The Helcim API will return a response as a JSON object for your website or application to consume, with relevant data objects or an errors object that outlines any errors that occurred. Some possible response types from the API include:

  • A single object
  • A transaction response object
  • An array of objects
  • An array of errors
Example transaction response from the Payment API

Example transaction response object from the Payment API