> ## Documentation Index
> Fetch the complete documentation index at: https://docs-dev-actions-triggers-prototype.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Manage Core Configuration

> Manage your login engine, iframe embedding, and custom HTML for your Login, Password Reset, and Multi-Factor Authentication screens.

The Core configuration page lets you manage the following settings for Universal Login and Classic Login:

* **Login engine**: Switch between Universal and Classic Login.
* **Iframe embedding**: Enable login flows to load inside iframes for development environments.

## Settings

### Universal or Classic Login

Choose which login experience your tenant uses. Changing this setting affects all applications that redirect to your Auth0 login page. To learn more, read [Universal Login vs. Classic Login](/docs/authenticate/login/auth0-universal-login/universal-login-vs-classic-login).

<Steps>
  <Step title="Navigate to Core configuration">
    Navigate to **Branding > Universal Login > Pro-code customizations** and select **Core configuration**.
  </Step>

  <Step title="Select login type">
    Under **Settings**, select **Universal Login** or **Classic Login**.
  </Step>
</Steps>

### Iframe embedding

Enable Universal or Classic Login to load when the application and login flow are embedded in an iframe, as with generative UI platforms like Vercel. When enabled, iframe embedding is only applied in development environments.

<Warning>
  When iframe embedding is enabled, security headers that protect against clickjacking are disabled.
</Warning>

<Steps>
  <Step title="Navigate to Core configuration">
    Navigate to **Branding > Universal Login > Pro-code customizations** and select **Core configuration**.
  </Step>

  <Step title="Enable iframe support">
    Under **Iframe settings**, toggle on **Enable support for generative UI platforms**.
  </Step>

  <Step title="Configure allowed origins">
    Under **Allowed iframe URLs for Login**, enter the allowed origins.

    For v0, enter the following origins:

    * `https://v0.app`
    * `https://*.v0.app`
    * `https://*.vusercontent.net`

    When an application is created from a generative UI platform such as Vercel using an available Auth0 integration, Auth0 pre-populates the allowed origins from the platform. Always verify the pre-populated origins to ensure completeness. To learn more, read [Integrate with Vercel](/docs/customize/integrations/integrate-with-vercel).
  </Step>
</Steps>

## Login

Customize the login page in Classic Login. To learn more, read [Customize the login page](/docs/customize/login-pages/classic-login/customization-classic).

## Password reset

Customize the password reset page in Classic Login. To learn more, read [Customize the Password reset page](/docs/customize/login-pages/classic-login/customize-password-reset-page).

## Multi-factor Authentication

Customize the multi-factor authentication page in Classic Login. To learn more, read [Customize MFA for Classic Login](/docs/secure/multi-factor-authentication/customize-mfa/customize-mfa-classic-login).