What is a Softphone?

A softphone is a software application, running in a web browser, a desktop app, or a mobile app, that makes and receives phone calls over the internet using SIP or WebRTC, in place of a physical desk phone. It registers to a telephony platform exactly the way a hardware phone does, so from the platform’s perspective a softphone is just another device.

How it works

A softphone establishes a SIP registration (for app-based softphones) or a WebRTC connection (for browser-based ones) to a SIP signaling layer over an encrypted transport, typically WSS (WebRTC over TLS) in the browser case. Once registered, it can place and receive calls like any SIP endpoint: audio is carried as SRTP, with STUN/TURN or a public media relay handling NAT traversal so calls connect even from behind restrictive networks. Because authentication is per-device, a softphone can be issued short-lived, revocable credentials rather than a long-lived shared password. It’s the same pattern used for embeddable, browser-based calling.

Why it matters

Softphones remove the dependency on physical hardware: agents can take calls from a laptop at home, a browser tab embedded in a CRM, or a mobile app, and a contact center can onboard a new agent by sending a link instead of shipping a desk phone. For developers, a browser-embeddable softphone (often shipped as an SDK) is what makes click-to-call, screen-pop, and in-app calling possible: the calling experience lives inside the product instead of a separate phone system.

FAQ

What is a softphone? A softphone is a software application, whether browser, desktop, or mobile, that makes and receives calls over the internet using SIP or WebRTC, registering to a telephony platform the same way a physical desk phone does.

What is the difference between a softphone and a desk phone? A desk phone is dedicated hardware registered to a SIP server; a softphone does the same job in software on a computer, browser, or mobile device, using a headset or the device’s built-in mic/speaker.