What Is a Soft Phone? How It Works, What You Need and Setup
What is a soft phone? A simple guide to how softphone apps make calls over the internet, what you need, free options, setup steps and common problems.
What is a soft phone? A soft phone (usually written softphone) is a phone app on your computer, tablet or smartphone that makes and receives calls over the internet instead of a phone line. It replaces a desk phone with software: you click a dial pad on the screen and talk through a headset. To call normal phone numbers, it connects to a VoIP account, usually through a standard called SIP.
Think about the last time you joined a work call from your laptop on a train or in a café. No desk, no handset, no cable, and yet the call came through your company’s main number. That is a softphone at work.
The “soft” simply means software, the opposite of “hard” physical equipment. This guide explains what a soft phone is in plain words: how a call travels, what you need, where it beats a desk phone, where it doesn’t, and how to set one up in about 15 minutes.
Jump to: Softphone vs other phones · How a call works · What you need · Examples · 15-minute setup · Fix common problems · FAQ
How Is a Soft Phone Different From a Desk Phone or Mobile?
| Feature | Softphone | Desk IP phone | Mobile phone |
|---|---|---|---|
| What it is | An app | A physical handset that plugs into the network | A device on the mobile network |
| Hardware cost | Just a headset | A handset for each desk | The phone itself |
| Works anywhere with internet | ✅ Yes | Usually tied to the office | ✅ Yes (mobile signal) |
| Uses your business number | ✅ Yes | ✅ Yes | Only with an app or forwarding |
| Depends on | Your computer and internet connection | Office network and power | Mobile coverage |
How Does a Softphone Call Actually Work?
Here is the life of one call, step by step:
- Sign-in: when you open the app, it registers with your provider’s server using your SIP username and password. This tells the server, “Calls for extension 204 can reach me here.”
- Dialling: you type a number. The app sends a SIP “INVITE” message, which works like a digital knock on the door.
- Voice to data: your microphone’s sound is compressed by a codec (a voice-packing method such as G.711 or Opus) and split into small data packets.
- The journey: the packets travel over the internet to the provider. If the person you’re calling has a normal phone, the provider passes the call into the public phone network.
- Hang-up: a “BYE” message ends the session.
SIP (Session Initiation Protocol) is the shared language most softphones and VoIP providers use. It is defined in the IETF’s RFC 3261. Because it is an open standard, most SIP softphones work with most SIP providers.
There is also a newer type: browser softphones. These run inside Chrome, Edge or Firefox with no install, using WebRTC. WebRTC became an official W3C and IETF standard on 26 January 2021.
A softphone is not a different kind of call. It is a different kind of handset, made of software.
What Do You Need to Use a Soft Phone?
- A device: a Windows PC, Mac, Linux computer, or an Android or iPhone.
- A softphone app: either from your phone system provider or a standard SIP app.
- A SIP or VoIP account: from your provider or your company’s phone system (PBX). It gives you a username, password and server address.
- A headset: a USB or Bluetooth headset with a microphone gives far clearer sound than laptop speakers and avoids echo.
- A stable internet connection: a voice call needs very little speed. Around 100 kbps per call is a common planning figure, but it needs a steady connection with low delay.
What Are Some Examples of Softphones?
Softphones come in three main types:
Not sure which phone service to pair your softphone with? Read our guide on how to choose the best business VoIP provider.
Who Uses Softphones, and Why?
- Remote and hybrid workers take calls on their business number from home, with no desk phone to carry.
- Call centres place agents’ calling next to their customer records on the same screen.
- Freelancers and small businesses get a professional second number without a second phone. See our guide on starting freelancing with no experience.
- Travellers keep one number wherever they have Wi-Fi.
Real-life example: a five-person accounting firm moves to a softphone app before tax season. Two staff work from home, but clients still call one office number. The call rings on everyone’s laptop, and whoever is free picks it up. No new handsets, no extra phone lines.
What Are the Pros and Cons of a Soft Phone?
| 👍 Pros | 👎 Cons |
|---|---|
| Low cost: no handset to buy | Needs a stable internet connection |
| Your business number on any device | Won’t work during a power cut or internet outage without a backup |
| Easy to add or remove users | Shares computer resources; a busy laptop can affect call quality |
| Works with CRMs and work apps | Emergency calls may not share your location automatically |
How Do You Set Up a Softphone in 15 Minutes?
- Get your SIP details from your provider or IT team: username, password, server (domain) and any port or transport settings.
- Install the app on your computer or phone.
- Add an account and enter the SIP details exactly as given. Most failures come from a typo here.
- Choose your audio devices: set the headset as both microphone and speaker.
- Allow microphone access when your system asks.
- Make a test call to your own mobile and listen for delay or echo.
- Record your voicemail greeting. Our professional voicemail greeting scripts make this easy.
How Do You Fix Common Softphone Problems?
| Symptom | Likely cause | Quick fix |
|---|---|---|
| “Registration failed” | Wrong username, password or server | Re-enter the details; check that the server address has no extra spaces |
| Call connects but there’s no sound in one direction | Router or firewall blocking voice traffic (often a NAT issue) | Try the provider’s recommended settings; ask IT to check the router |
| Robotic or broken voice | Unstable Wi-Fi or a busy connection | Use a cable, move closer to the router, or pause large downloads |
| Echo | Laptop speakers feeding into the microphone | Use a headset |
| Missed calls on mobile | The phone puts the app to sleep | Allow notifications and turn off battery saving for the app |
Is a Softphone Secure?
It can be, if you set it up well. Choose apps that support encryption (look for TLS for sign-in and SRTP for the voice itself), use a strong unique SIP password, and keep the app updated. A stolen SIP login can be used to run up expensive call charges. For a wider view of protecting business systems, see our article on how threat actor profiling optimises security spend.
Frequently Asked Questions
Is softphone one word or two?
Both are used. “Softphone” is the common industry spelling, but “soft phone” means the same thing.
Is a soft phone free?
Many softphone apps are free, but calls to normal phone numbers usually need a paid VoIP or SIP account. App-to-app calls are often free.
Can I use a softphone on my mobile?
Yes. Most providers and SIP apps have Android and iPhone versions. Calls use Wi-Fi or mobile data.
Do I need a special headset?
No, but a USB or Bluetooth headset with a good microphone greatly improves sound and stops echo.
What is the difference between a softphone and VoIP?
VoIP is the technology that carries voice over the internet. A softphone is one of the devices (an app) you use to make VoIP calls.
Your Softphone Starter Checklist
- Decide what you need: a provider app for a team, or a SIP app for one account.
- Get your SIP username, password and server details.
- Install the app and connect a headset.
- Run a test call to your mobile.
- Turn on encryption (TLS and SRTP) if your provider supports it.
- Set up voicemail and call forwarding to your mobile for outages.
- Keep a mobile phone ready for emergency calls.
So, what is a soft phone? It is simply your desk phone turned into an app, and it lets your business number follow you anywhere you have internet. Set it up once, test it well, and it can replace the desk phone for most everyday calls.
