> ## Documentation Index
> Fetch the complete documentation index at: https://docs.rownd.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Adding cross-domain authentication

> Keep users signed in across all of your web properties

Rownd's cross-domain authentication provides a seamless user experience across multiple domains and subdomains without third-party cookies. This modern approach maintains secure user sessions across your entire digital ecosystem.

## How It Works

Rownd uses a novel authentication method that:

* Operates independently of third-party cookies

* Maintains sessions across different domains

* Synchronizes user state automatically

* Preserves security while improving user experience

## Benefits

* **Seamless User Experience**: Users stay signed in across all your properties

* **Cookie-Independent**: Future-proof against browser privacy changes

* **Flexible Implementation**: Works across web apps, mobile apps, and websites

* **Improved Conversion**: Reduces friction in user journeys

* **Enhanced Security**: Maintains secure sessions without compromising user privacy

## Common Use Cases

### Landing Page to Application

1. Add Rownd to your marketing site

2. Enable passive authentication (e.g., Google One Tap)

3. Users automatically sign in when accessing your main application

4. Increases conversion by removing authentication barriers

### Documentation Portal Integration

1. Implement Rownd across your documentation site

2. Provide personalized help based on user context

3. Track documentation usage patterns

4. Deliver customized content based on user preferences

### Multi-App Ecosystem

1. Deploy Rownd across multiple applications

2. Maintain consistent authentication state

3. Works seamlessly with [sub-brands](https://docs.rownd.io/configuration/customizations/sub-brands)

4. Create branded experiences for different user segments

To implement cross-domain authentication within your product, follow our[ implementation steps.](/configuration/cross-domain/implementation)

## SDK References

For detailed implementation guidelines, refer to:

* [Web SDK Documentation](https://docs.rownd.io/sdk-reference/web)

* [Mobile SDK Documentation](https://docs.rownd.io/sdk-reference/mobile)

* [Sub-brands Configuration](https://docs.rownd.io/configuration/customizations/sub-brands)