# API Reference
source: https://developer.mastercard.com/merchant-self-services/documentation/api-reference/index.md

### Versionless API {#versionless-api}

A versionless API is one that remains backwards compatible as new features or enhancements are added. Using a versionless API is a critical part of how we designed Ethoca Merchant Self Services as it allows for faster and more seamless ways for new features or improvements to be added without impacting existing integrations or end-user experiences.

The term *versionless API* doesn't mean there are no versions of the API. Instead, it refers to the fact that the API doesn't require customers to manage traditional version upgrades to avoid their integration from being broken upon a new release.

There might be times when updates to the API introduce the need for customers to make changes to their integration, such as removing a data field. But these instances are very rare and would be communicated well in advance of the change taking place.

## Environment Domains {#environment-domains}

Note: If you are already using the api.mastercard.com URL in your sandbox or production environments, you can continue to do so.
* Sandbox
* Production

```Sandbox
https://sandbox.api.ethocaweb.com/ethoca/merchant-self-services
```

```Production
https://api.ethocaweb.com/ethoca/merchant-self-services
```

## APIs {#apis}

Note: The API request below shows example data for each individual field. Test cases are available to use in the sandbox, which include sets of request data that return expected responses. Contact your integration representative for details.
API Specification: `https://static.developer.mastercard.com/content/merchant-self-services/swagger/merchant-self-serve-api-spec.yml`

### Error handling {#error-handling}

See [Code and Formats](https://developer.mastercard.com/merchant-self-services/documentation/code-and-formats/index.md) for detailed information about error response handling for the Merchant Self Services API.