What is CMCD?

Common Media Client Data (CMCD) is a specification that allows streaming video players to share information about their playback environment and behavior with the CDN (Content Delivery Network) serving the video. This feedback loop can help the CDN make more intelligent decisions about how to deliver content, potentially improving the user's viewing experience.

CMCD, developed under the auspices of the Streaming Video Alliance, provides a standard method for this communication. It defines a set of key-value pairs that the player can send to the CDN in HTTP requests. These include details such as the player's buffer length, the bitrate of the video, the duration of the video, the encoded frame rate, and other similar technical parameters. The CDN can then use this data to better manage network resources and optimize delivery to that particular client.

Video streaming definitions