An MCU performs the decode-mix-encode pipeline that an SFU avoids. Each participant uploads their stream to the MCU; the MCU decodes all streams, composes them into a single mixed video (typically a grid layout) plus a mixed audio track, encodes the result, and sends one encoded stream to each participant. From the participant's perspective the experience is identical to receiving a single TV broadcast — no client-side composition needed.
The advantage of MCU is bandwidth efficiency on the receiver side: each participant downloads one stream regardless of how many are speaking. This used to matter on the early-2000s narrowband connections where MCU originated. The disadvantage is CPU cost on the server — decoding and re-encoding 30 HD streams at 30 fps requires significant horsepower, scaling cost linearly with participants × time.
In 2026, MCUs are rare in pure WebRTC. SFUs dominate because they have much lower server CPU cost and let receivers compose layouts locally. MCUs persist in legacy SIP/H.323 video-conferencing systems, in services that need to record a single composed stream (one MP4 file with the grid), and in services that need to stream a video conference out to non-WebRTC platforms (where HLS/DASH receivers need a single composed stream). Some platforms offer MCU as a recording-only adjunct to their main SFU.
The book · Volume 3 of 7
Video Streaming: A Complete Guide to Video Delivery: From ABR and CDNs to Players, WebRTC, DRM, and the Economics of Streaming
An MCU gives every participant one mixed stream, which helps weak clients and SIP gateways, but the decode-mix-encode loop makes server CPU the main cost driver. This volume covers MCU and SFU topologies in detail, with WebRTC media servers, real-time latency, simulcast and the per-participant economics of conferencing. Written by Nikolay Sapunov, CEO at Fora Soft.
Deciding whether an MCU, an SFU or a hybrid fits your conferencing product?
Describe your call sizes and client devices and we will give you a topology recommendation with a server cost estimate per participant-hour for MCU versus SFU. 250+ video products shipped since 2005.
