The present invention teaches a method and system for dynamically inserting content into a streaming media program. The system and method provide a program manifest to rendering devices requesting a streaming media program and that manifest can include URIs which point to main program content on a content delivery network and includes meta URIs (mURIs) which point to a dynamic content decisioning server. The dynamic content decisioning server receives requests for the content indicated by the mURIs and operates to dynamically select content, from a dynamic content delivery network, to fulfill the requests. The selection can be based upon a variety of criteria, including viewer and/or rendering device demographics, advertiser campaign strategies, etc. Thus two or more rendering devices playing streaming media defined by the same manifest may render different inserted content for their viewers. Similarly, a program rendered from a manifest at one point in time may have different inserted content than the same program rendered by the same rendering device at another time.