# Set up CDN mapping in MediaTailor
<a name="cdn-mapping-mediatailor"></a>

This section explains how to configure AWS Elemental MediaTailor to use your content delivery network (CDN) domain names. After setting up your CDN routing behaviors, you need to update your MediaTailor configuration to ensure that manifests reference your CDN domain instead of directly referencing origin servers.

Configuring CDN mapping in MediaTailor ensures that all content and ad segment URLs in your manifests point to your CDN rather than directly to origin servers. This step is essential for creating a complete CDN delivery chain and maximizing the benefits of your CDN integration.

## CDN mapping configuration in MediaTailor
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After setting up your CDN routing behaviors, configure MediaTailor to use your CDN domain names:

1. Open the [MediaTailor console](https://console.aws.amazon.com/mediatailor/home).

1. Select the configuration you want to update.

1. In the **Advanced settings** of the **CDN configuration** section, enter your CDN domain name in the **CDN content segment prefix** field.

1. If you're using a separate CDN domain for ad segments, enter it in the **CDN ad segment prefix** field.

1. Save your changes.

This configuration ensures that MediaTailor generates manifests with URLs that point to your CDN instead of directly to the origin or ad segment storage.

### Understanding base URL behavior
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MediaTailor determines base URLs in manifests based on your CDN prefix configuration:
+ **CDN ad segment prefix configured**: Ad segments use the CDN prefix as the base URL.
+ **CDN ad segment prefix not configured**: Ad segments use the direct MediaTailor location as the base URL.
+ **CDN content segment prefix configured**: Content segments use the CDN prefix as the base URL.
+ **CDN content segment prefix not configured**: Content segments reference the original content origin.

#### DASH BaseURL handling
<a name="dash-baseurl-handling"></a>

For DASH manifests, MediaTailor manages `BaseURL` settings differently for content and ad segments:

**Content segments:**
+ **With CDN content segment prefix**: MediaTailor sets exactly one `BaseURL` at the `MPD` level using your specified prefix.
+ **Without CDN content segment prefix**: MediaTailor preserves existing `BaseURL` settings from the origin manifest, or adds one based on the origin `MPD` URL if none exist.

**Ad segments:**
+ **With CDN ad segment prefix**: Each ad period gets exactly one `BaseURL` using the configured prefix.
+ **Without CDN ad segment prefix**: Each ad period gets exactly one `BaseURL` pointing to the MediaTailor ad content server.

**Example CDN mapping example**  
If your content origin is `http://origin.com/contentpath/` and your CDN content segment prefix is `https://cdn.example.com/`, then a content segment that would normally be referenced as `http://origin.com/contentpath/subdir/content.ts` will appear in the manifest as `https://cdn.example.com/subdir/content.ts`.

## Important considerations
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When configuring CDN mapping in MediaTailor, keep the following important considerations in mind:

**Use HTTPS for CDN prefixes**  
Always use HTTPS URLs for your CDN prefixes to ensure secure content delivery.

**Match CDN behavior paths**  
Ensure that the CDN prefixes you configure in MediaTailor match the path patterns you configured in your CDN behaviors.

**Consider regional CDNs**  
If you're using different CDN domains for different regions, you'll need to create separate MediaTailor configurations for each region.

**Verify domain ownership**  
Ensure that you have control over the CDN domains you configure in MediaTailor.

## Verify CDN mapping configuration
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After configuring CDN mapping in MediaTailor, verify that your configuration is working correctly:

1. Request a manifest through your CDN.

1. Examine the manifest content to verify that segment URLs reference your CDN domain.

1. Check that content segment URLs in the manifest point to your CDN domain.

1. Check that ad segment URLs in the manifest point to your CDN domain.

For comprehensive testing and validation procedures, see [Testing and validation for CDN and MediaTailor integrations](cdn-integration-testing.md).

## Next steps
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After configuring CDN mapping in MediaTailor, the next step is to implement security best practices for your CDN integration. See [CDN integration security best practices for MediaTailor](cdn-security-best-practices.md) for instructions.