Verifying Client Media Playback using Unique Embedded Metadata

The described subject matter is directed to injecting metadata into a media stream at (or just after) a cache edge of a content delivery network (“CDN”). A unique instance value (e.g., included within a tag or uniform resource locator (“URL”)), is embedded by an edge device into metadata for the media stream. Examples of media stream metadata include, but are not limited to, D3 timed metadata inserted in an MPEG-2 transport stream or an emsg box in the ISO-BMFF video container for MPEG-DASH. When a streaming media player receives the metadata, it generates a network request or callback request including the tag or directed to the embedded URL. A server receiving this message can use the unique instance value as confirmation that the player received and processed the metadata, which indicates that media content delivered with the metadata was presented by the media player. The server can then authorize additional media delivery and/or generate reliable presentation statistics for the content