A Content Decryption Module is an implementation of proprietary DRM client code inside a browser that lies behind the standardized Encrypted Media Extensions (EME) implementation. As originally conceived, any browser could support multiple CDM implementations, but politics and commercial rivalry has limited each of today's commercial offerings to support of one single CDM and therefore a single DRM format. Given the way that MPEG-DASH streams and the use of CENC interact, this is not as limiting as it may sound - but it is important to operate an MPEG-DASH video service alongside a multi-DRM service to provide a seamless consumer playback experience.