CU-RTC-Web (Customizable, Ubiquitous Real-Time Communication over the Web) was a competing proposal to WebRTC submitted by Microsoft to the W3C in 2012.
What CU-RTC-Web proposed
CU-RTC-Web proposed a lower-level API approach that gave developers more direct control over the media pipeline, without relying on SDP for session negotiation. Key ideas included:
- Object-oriented API instead of SDP-based negotiation
- More granular control over codecs, transport, and media processing
- Closer alignment with Microsoft’s existing real-time communication stack
CU-RTC-Web’s legacy
While CU-RTC-Web itself was not adopted, its object-oriented approach heavily influenced:
- The ORTC (Object Real-Time Communications) specification
- Parts of the WebRTC 1.0 API that moved toward more programmatic control (RTCRtpTransceiver, RTCRtpSender/Receiver)
- The broader discussion about reducing WebRTC’s dependence on SDP
CU-RTC-Web is now only of historical interest. Microsoft eventually adopted standard WebRTC in Edge (after switching to Chromium) and contributed to the ORTC specification instead.
