The three kinds, and which one you are actually choosing
The app that comes with your platform. RingCentral, Dialpad, SoundLine, Grasshopper, Ooma and the rest each ship their own. You do not pick it separately; it comes with the service. For most businesses this is the whole decision, and judging it means judging the platform.
A standalone SIP softphone. Zoiper, Linphone, MicroSIP and similar. These connect to any provider that gives you SIP credentials. They are useful when you want one app across several providers, when you need something very light, or when your provider's own app is poor. They put the configuration on you.
A free consumer app with a number attached. Google Voice and similar. A number and an app rather than a business phone system, with the limits covered on their own page.
Choosing between the first two is the only real fork. If your provider's app does the job, use it. A standalone SIP client is a fix for a specific problem rather than an upgrade.
The five things that decide whether it works
Judge any softphone, from any provider, on these. In this order.
1. Does it ring when the phone is locked? The single most common failure, and almost nobody tests it before committing. Mobile operating systems suspend background apps, and a softphone that is not built to wake properly misses calls silently. Test it: have someone call you with the app closed and the phone locked. If it misses, nothing else on this list matters.
2. Does it hand over between devices cleanly? Starting a call on a laptop and moving it to a mobile without hanging up is the thing that makes a softphone better than a handset rather than merely cheaper.
3. Is the call quality steady on a mediocre connection? Not the best-case quality. Test it on hotel wifi, on mobile data, on the connection you will actually be using. Voice needs about 100 kbps each way, and upload is usually the limiting factor.
4. Can you tell which line a call came in on? If you run more than one business, or you have a personal and a business number in the same app, answering as the right company depends on the app telling you before you pick up.
5. What does it do when it has no connection? The call does not vanish; it arrives at your provider. Whether it then reaches you depends on a forwarding rule you set in advance. An app that makes that rule easy to find is worth more than one with a nicer interface.
Features that matter less than people expect: the visual design, the number of integrations you will never switch on, and anything described as AI that sits on a tier you are not buying.
When a free softphone is enough
If you have SIP credentials from a provider and want a lightweight client, the free standalone apps are genuinely good and you should not pay for an alternative. They are a reasonable choice for a technically comfortable user with simple needs.
What you give up is the layer around the app: routing, hours, voicemail transcription, a shared number, desk phone provisioning, and somebody to call when a call does not connect. If those are not things you need, a free client and a cheap SIP provider is a sound setup.
Where SoundLine's app sits
Ours comes with the platform rather than being sold separately. It runs on desktop and mobile, rings both at once or in an order you set, shows which business a call is for before you answer, and hands calls between devices. The platform behind it is the part we would actually argue for: carrier-registered texting, routing, desk phones, and a separate identity for each business you run.
What it is not. It is not a standalone SIP client you can point at another provider, and we do not claim it beats every app in the category on interface design. If you want a universal SIP client, use one of the free ones and pick a provider on the strength of the service.
Questions people ask
What is the best softphone?
For most businesses it is whichever one comes with the phone platform they choose, because softphones are rarely bought separately. The useful test is whether it rings when the phone is locked, hands calls between devices, holds up on a weak connection, shows which line a call arrived on, and makes the no-connection rule easy to set.
Is there a good free softphone?
Yes. Several free standalone SIP clients are well built and work with any provider that supplies SIP credentials. What they do not include is routing, voicemail transcription, shared numbers or support.
What is the best softphone for Android?
The same test applies, and on Android the background activity question matters most. Whichever app you choose, allow background activity and notifications for it, then test with the phone locked.
Do I need a softphone and a desk phone?
Most businesses end up with both, ringing the same number. The app goes where you go; the handset stays on the counter for whoever walks up to it.
Can a softphone replace a business phone system?
No. A softphone is the interface. The phone system is the number, the routing, the texting registration and the network behind it.
Try ours with the five tests
Seven days, a real business number, the app on every device you want it to ring. Run all five tests on it.