What Is WebRTC and How Does 3CX Use It for Browser-Based Calling?

Author : Andrew Johns | Published On : 17 Aug 2026

If you have used a video call in a web browser, you may already have used WebRTC without knowing it.

WebRTC (Web Real-Time Communication) is a web technology for real-time audio, video and data on a web browser without requiring a separate plugin. You can use WebRTC in modern browsers, and it is the underlying technology for many browser-based communication tools.

3CX phone system uses WebRTC technology to let you make and receive calls using your web browser. This means you have your computer as a phone without relying on a traditional desk phone or installing a separate desktop softphone.

But there is an important point to understand:

WebRTC is not the phone system itself, but the technology that allows the browser to handle real-time communication. 3CX offers a phone system that connects browser-based calls to the rest of the telephone network.

What is WebRTC?

WebRTC means Web Real-Time Communication. Think of it as an open web standard that lets browsers and apps exchange audio, video and data in real time. WebRTC allows devices to communicate directly with each other, a model known as peer-to-peer (P2P) communication.

For example, when a website asks:

Have you ever accessed a site and needed to make a call or record audio? It asks: “Allow this site to use your microphone?”

It is WebRTC technology trying to access your microphone for a real-time call.

WebRTC can support:

• Voice calls

• Video calls

• Screen sharing

• Data exchange

• Real-time communication between devices

Modern browsers such as Chrome, Edge, Firefox and Safari support WebRTC.

Is WebRTC a VoIP service?

No.

WebRTC is a technology used for real-time communication in a browser. VoIP, or Voice over Internet Protocol, is a technology for sending voice calls over an internet connection. WebRTC can be used to make VoIP calls directly from a browser.

A service such as a 3CX phone system or a VoIP phone system can use WebRTC as the browser-side technology, while the phone system manages extensions, call routing, SIP trunks, queues, and other business calling functions.

Put simply: 

WebRTC = the technology that sends and receives audio in real time through your browser, so you and the other person can hear each other.

3CX = the phone system that manages the business call.

How does 3CX use WebRTC?

3CX uses WebRTC in its Web Client to turn your browser into a phone. WebRTC lets the browser use your microphone and speakers to send and receive audio during the call.

After logging in to the 3CX Web Client, you can choose Browser as your preferred device to make a call. Then use your browser's microphone and speakers to communicate. 

The Web Client offers businesses more than just communication features. It is also for call transfers, conferencing, call recording (where permitted), presence information, and video calling.

What happens when you make a browser call?

You -- Browser/WebRTC -- WebRTC -- 3CX phone system -- Phone network or another 3CX user

Here is what happens:

1. You log in to the 3CX Web Client.

2. You enter a number or select a contact to call.

3. Your browser accesses your device’s microphone and speakers.

4. WebRTC gives your browser access to your microphone and handles the real-time audio connection for the call.

5. 3CX processes the call and sends it to the correct destination.

6. The other person answers the call.

7. Your voice is transmitted in real time over the internet.

8. You and the other person can then hear and speak to each other.

Does 3CX WebRTC replace a desk phone?

It can. You can make and receive calls directly from a browser. Why do you need a traditional desk phone? 

This is how 3CX describes its Web Client:

To handle calls, check colleagues' statuses, respond to messages, and make video calls without relying on a traditional desk phone.

For many office workers, the setup can be as simple as:

• A computer

• A supported web browser

• A headset or built-in microphone and speakers

• An internet connection

• Access to the company's 3CX system

Still, some users prefer calling with physical handsets, especially receptionists, employees who want dedicated phone controls, and so on.

What do you need to make a 3CX browser call?

1. A 3CX account

Your business needs to set up a 3CX system by an administrator who must provide you with access to the Web Client.

2. A supported browser

You can use a supported browser such as Firefox, Chrome, or Edge. WebRTC is built into modern browsers, enabling Web Client to make calls on your browser. 

3. A microphone and speaker

A headset is usually the better option for business calls because it can reduce background noise and help prevent other voices from being picked up by your microphone.

4. A stable internet connection

Because the call is carried over the internet, you need a stable internet connection. 

5. Browser permissions

You need to grant your browser permission to access your device’s microphone. If not, you cannot send audio streams when on call.

Can 3CX WebRTC call mobile and landline numbers?

Yes, when the 3CX system is connected to a suitable SIP trunk or other telephone service.

A caller can use WebRTC on the browser side. At the same time, the receiver uses a mobile phone, which does not necessarily use WebRTC.

Employee's browser -- 3CX -- SIP trunk -- mobile network -- customer's phone

So 3CX uses a SIP trunk to connect calls to the regular phone network, allowing one to call mobile and landline numbers.

3CX documentation states that businesses need a SIP trunk provider that supports telephone numbers and external inbound and outbound calling.

What is the difference between WebRTC and SIP?

WebRTC and SIP are often mentioned together, but they mean different things and function in entirely different ways. 

WebRTC is a web technology that enables real-time communication in browsers, such as sending and receiving audio during a call.

SIP (Session Initiation Protocol) is a signalling protocol commonly used to set up, manage and end VoIP calls.

What are the benefits of WebRTC calling with 3CX?

No separate phone required

There is no need to call from a desk phone; employees can use their computers and headsets.

No traditional softphone installation

The Web Client runs in the browser, which can make deployment simpler for businesses.

Easier remote working

An employee working remotely can access the company's 3CX Web Client on a supported device and use it as a business communication interface.

One browser-based workspace

Users can manage calls and other communication functions from the Web Client, rather than switching between several applications. 3CX also supports CRM integrations, offering click-to-call features that help users initiate calls from websites and CRM systems.

Useful for customer-facing teams

Sales and support teams can keep their CRM, email, customer records and phone interface on a computer. And still call with it, accessing those records in real-time.

What are the limitations?

WebRTC calling is useful, but it is not magic.

Your internet connection matters; without it you cannot make calls. So a poor network can result in delays, interruptions or poor audio.

The bottom line

WebRTC lets a browser access your microphone and camera and send and receive audio and video during a call. 3CX manages the phone system and routes calls to another user or to a different phone number.

For businesses, this makes browser-based calling simple, especially for remote and hybrid teams. 

In simple terms: WebRTC handles real-time audio and video data needed to make the call. 3CX manages the call.