# MediaTailor domain variables for multiple content sources
<a name="variables-domains"></a>

AWS Elemental MediaTailor dynamic domain variables allow you to use multiple domains, such as the **my-ads-server.com** part of the URL http://my-ads-server.com, with the player parameters in your configuration. This makes it possible for you to use more than one content source or ad decision server (ADS) in a single configuration. 

 You can use domain variables with any parameter that contains a URI: 
+ `AdDecisionServerUrl`
+ `AdSegmentUrlPrefix`
+ `ContentSegmentUrlPrefix`
+ `LivePreroll.AdDecisionServerUrl`
+ `VideoContentSourceUrl`

 Domain variables are used alongside *configuration aliases* to perform dynamic variable replacement. Configuration aliases map a set of aliases and values to the player parameters that are used for dynamic domain configuration. For setup procedures, see [Creating and using configuration aliases with MediaTailor](creating-configuration-aliases.md). For detailed reference information, see [MediaTailor configuration aliases overview](configuration-aliases-overview.md).