> For the complete documentation index, see [llms.txt](https://nivapay.gitbook.io/product-and-api-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://nivapay.gitbook.io/product-and-api-documentation/integrations/authentication.md).

# Authentication

Public endpoints do not require an authentication header. However, for calling protected API endpoints you need an API Key. All requests to protected endpoints must contain the following header.

&#x20;<mark style="color:purple;">X-API-KEY: \<api\_key></mark>

Once you onboard with Nivapay as a merchant, you will receive merchant ID and API key combination each for Sandbox and Production environments.