> For the complete documentation index, see [llms.txt](https://docs.rocketfuel.inc/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rocketfuel.inc/developer-guides/api-reference/payins/authentication.md).

# Authentication

- [Authenticate a merchant](https://docs.rocketfuel.inc/developer-guides/api-reference/payins/authentication/authenticate-a-merchant.md)
- [Authentication Without Email / Password](https://docs.rocketfuel.inc/developer-guides/api-reference/payins/authentication/authentication-without-email-password.md)