WebRTC was born to do one thing really well – establish low-latency, high-security multimedia connections directly between browsers and devices. Yet its greatest strength has always been flexibility.
Even in 2025, when you set out to build a video conferencing application, the options remain wide open: go full peer-to-peer, deploy one (or many) media servers, or combine everything exactly the way your product demands.
You can cherry-pick features and still find several technical paths to implement them. You can run a single beefy single backend or spin up an almost infinitely scalable grid using proven patterns.
With all that freedom, choosing the optimal path can feel paralyzing. This guide clears up the classic P2P vs MCU vs SFU debate once and for all – straight from developers who have shipped dozens of real-world solutions.
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Key Takeaways
- P2P is unbeatable for tiny groups but collapses under its own weight past ~4–5 participants.
- SFU is the sweet spot for most modern group apps and scales beautifully with proper architecture.
- MCU shines when you have many passive viewers or need to support very weak client devices.
- 2025 reality: almost every serious product ends up as a hybrid that starts in P2P and seamlessly promotes to SFU or MCU as participants join.
- Pick based on your maximum concurrent speakers per room, target device specs, and must-have server features.
What is P2P – Peer-to-Peer?
Imagine it’s Christmas and you have a bunch of friends scattered across town. No one has time for a big gift-exchange party, so you agree that everyone will simply drop by each other’s houses. You visit them, they visit you – pure peer-to-peer gift delivery.
In a WebRTC call that works exactly the same way: every participant connects directly to every other participant. The signaling server is nothing more than an address book that helps everyone find each other; after that, the media flows straight between devices.
This pattern works beautifully as long as:
- your group stays small (ideally 2-4 people)
- everyone can physically reach everyone else (no nasty firewalls or NATs blocking the way)
The math gets brutal fast. With 4 people, each participant handles 6 connections (3 outgoing + 3 incoming). With 5 people, it’s already 8 connections each. At 6 participants, you’re juggling 10.
Every single stream has to be encoded and uploaded or received and decoded in real time, eating CPU, network bandwidth, and battery. A 10-on-10 Full HD call in pure P2P can easily demand 50 Mbps upload/download per device and hammer even a decent CPU.
Then come the connectivity headaches. Picture one friend moving into an upscale gated community: they can drive out to you, but you can’t drive in to them. Corporate networks, symmetric NATs, and VPNs create exactly that situation: one-way or no-way reachability. Without a TURN server as a fallback, some users simply never see each other.
Finally, there’s the “group photo” problem: if you want to pile all gifts together for a big Instagram shot, every single person has to assemble the pile themselves because the gifts are scattered at everyone’s homes. In P2P, there is no central place for server-side recording, cloud transcription, analytics, or any once-per-call feature is impossible without extra tricks.
Real-world P2P examples
Secure 1:1 mobile video calling apps (like Tunnel) and early versions of Google Meet (before they added server features) rely heavily on P2P.
WebRTC media servers: MCU and SFU
When the friend group gets too big and the driving-around madness becomes unbearable, you rent the local coffee shop to act as a central gift hub. Everyone drops off gifts there and picks up whatever is waiting. That’s exactly what a WebRTC media server does: it becomes the single point that receives streams and redistributes them.
A few years ago, servers were strictly either SFU or MCU. Today, almost every serious open-source (Janus, Mediasoup, Kurento, Jitsi) and commercial solution supports both modes, so SFU and MCU are now feature sets rather than product categories.
What is SFU – Selective Forwarding Unit?
The coffee shop bartender keeps track of every new gift that arrives and phones the recipient: “Hey, one new package for you.” You drive over, grab it, go home. Three new gifts = three phone calls = three trips. Alternatively, you can just pop in every few minutes and check yourself.
That’s SFU in a nutshell: each participant sends their stream once to the server. The server clones the stream and selectively forwards it to whoever needs it. Clients end up with dramatically lower load:
- 4 users → 1 upload + 3 downloads (instead of 3+3 in P2P)
- 10 users → 1 upload + 9 downloads (instead of 9+9)
The “selective” part means the server maintains a separate WebRTC connection for every single outgoing stream. A 10-person room creates 10 ingest + 90 outgoing connections on the server – still manageable up to ~20–30 active speakers.
SFU Scalability – the killer feature
When the coffee shop gets swamped, you simply open more branches and forward packages between them. Routing rules can be as clever as you want: geographic, load-based, customer-segment-based. That’s why SFU backends scale almost infinitely horizontally: spawn new nodes, redistribute streams, done.
Real production setups often split ingest nodes (receiving streams from speakers) and edge nodes (delivering to viewers), so a flood of passive watchers never affects the broadcasters.
SFU examples
Skype, WhatsApp, Telegram, Discord – pretty much every messenger with group video calls and recording uses SFU under the hood. Separate streams give you per-participant quality adaptation, spotlight modes, and rock-solid behavior on cellular.
What is MCU – Multipoint Control Unit?
The coffee shop owner gets tired of endless phone calls and hires Christmas wizards: every new gift magically appears inside a huge labeled crate at the recipient’s home. You only make one trip to pick up one giant box that already contains everything addressed to you. Rearranging the order inside the box for your partner? Impossible – everyone gets the same layout.
MCU merges all incoming video and audio streams into a single composite stream per participant (excluding their own feed to prevent echo). A 10-person call now needs only 20 server connections total (10 in + 10 out). That’s why even a cheap laptop can comfortably join a 100-person Zoom call.
The magic is expensive: real-time compositing, mixing, and loudness normalization are extremely CPU-heavy. Need different layouts for mobile vs desktop? You have to composite twice. Want a custom grid because someone pinned a speaker? Composite again.
MCU scalability
Far more limited than SFU because you can’t easily split a single composite across machines without noticeable delay. The usual trick is to let MCU handle the heavy mixing and then hand the finished stream to an SFU grid for distribution.
MCU examples
Classic Zoom gallery view, Webex, GoToMeeting, and most webinar platforms run MCU or MCU+SFU hybrids for large audiences.
TL;DR – Quick Decision Table
1-4 users per room → P2P
Pros: lowest idle cost, fastest to market, potentially most secure
Cons: high bandwidth on mobile, no server-side recording or analytics
5-20 users → SFU
Pros: excellent horizontal scaling, full server-side features, great UX flexibility
Cons: still client-heavy, recording sometimes needs extra MCU step
20+ users → MCU or MCU+SFU
Pros: minimal client load, works on low-end devices, trivial recording
Cons: highest server cost, limited per-call customization
FAQ
Is pure P2P still used in 2025?
Yes, for 1:1 and very small groups where cost and privacy are paramount.
Can I record a pure P2P call?
Only client-side (which is messy) or by forcing a “silent” participant that is actually a server bot.
Which is cheaper to run – SFU or MCU?
SFU is almost always cheaper at scale because you can distribute load horizontally. MCU becomes economical only when you have huge audiences of viewers with weak devices.
Do I need both SFU and MCU?
Many teams run SFU as the main workhorse and spin up temporary MCU instances only for recording or for very large broadcast-style rooms.
What about security differences?
WebRTC encrypts media everywhere, but SFU/MCU servers become extra attack surface. Modern setups use per-session keys, Insertable Streams, and strict token auth to stay safe.
Conclusion
P2P, SFU, and MCU are not competitors; they are tools in the same toolbox. The smartest architectures today dynamically choose the right tool for the current room size and feature set. Understanding the trade-offs lets you build systems that are fast, cheap, and reliable without painting yourself into a corner later.
Want to go deeper? Check our other technical posts:
- How to keep latency under 1 second for mass streams
- WebRTC on Android deep dive
- WebRTC security explained in plain language
Still have questions or ready to design your own hybrid backend? Drop us a line or book a consultation today. We’ll help you map out the fastest, most efficient path from idea to live product that fits your timeline, budget, and requirements.
⚙️ Learn more about our WebRTC Development Expertise
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