# API Onboarding Process
source: https://developer.mastercard.com/mastercard-processing-core/documentation/api-onboarding/index.md

The Mastercard Processing API is self-service and can be tested using our Sandbox testing solution. Follow steps in the [Quick Start Guide](https://developer.mastercard.com/platform/documentation/getting-started-with-mastercard-apis/quick-start-guide/) to create a Mastercard Developers account, set up a project, download the Sandbox keys, generate your own API client (or use the provided [Reference Application](https://developer.mastercard.com/mastercard-processing-core/documentation/reference-app/index.md)), and test your API.

If you have tested in our Sandbox and want to move forward with us by testing our solution in MTF, contact us at \[contact\] to start the onboarding process.

The API onboarding process begins when we determine your business needs and customize a setup of our CMS for you. The next phase includes integration and testing.

## Connection and Integration {#connection-and-integration}

There are two ways of integrating with the Mastercard Processing CMS:

* **An API client generated by Mastercard**: Create a customizable API client from the MP OpenAPI Specification (OAS) and let the Mastercard open-source client libraries handle authentication for you. This approach offers more flexibility and is strongly recommended. For more information, see \[Generating and Configuring the Mastercard API Client\].
* **Any method of your choice** : Use the HTTP client of your choice and leverage the Mastercard open-source [client libraries](https://developer.mastercard.com/platform/documentation/security-and-authentication/using-oauth-1a-to-access-mastercard-apis/#client-libraries) for signing your requests. For more information, see [API Reference](https://developer.mastercard.com/mastercard-processing-core/documentation/api-reference/index.md).