> For the complete documentation index, see [llms.txt](https://developers.citrusad.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developers.citrusad.com/integration/reference/authentication-1.md).

# Authentication

{% hint style="info" %}
Epsilon Retail Media's documentation is now centralized with our knowledgebase!

For up to date guides, please view [this page](https://help.citrusad.com/retail-media-interface/integration/brand-pages/brand-page-retailer-integration-guide/authentication-1) in the new Integration APIs space of our documentation.
{% endhint %}

Brand Pages uses the same API key as the Epsilon RMN platform; no separate key is required.

Requests include an `Authorization` header using HTTP Basic authentication, with the API key encoded according to the Request for Comments (RFC) specification:

```apache
/Authorization: Basic base64(<apiKey>:)
```

In addition to the RFC-defined format above, the platform also supports passing the existing API key value directly in the `Authorization`header for compatibility with established client integrations.

```apache
Authorization: Basic \<existing_api_key>
```

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