What is SIP?

SIP (Session Initiation Protocol) is a common form of internet telephony protocol (IP telephony), and provides the basis in terms of the structure of all types of communications sessions over the internet. More specifically, it creates the sessions, monitors signals between users, and also cuts off connections between users, once the sessions have ceased.

SIP is inherent in voice calls and video calls, and enables users to send messages to each other, but does not send other forms of information. SIP apps can be installed on smartphones and other mobile devices, and once connected with a VoIP service provider, can enable the user to become remote.

So if you’re not present in the office, and you receive a call, both your office phone and your mobile will be contacted, and this is made possible by installing the SIP app.

It is important to remember that while VoIP service providers such as freezvon.com (who offer their clients a virtual phone number, together with, a range of other internet call services) offer SIP as part of their services, this is actually only one part of the range of technologies that the umbrella term VoIP (Voice Over Internet Protocol) covers. This is because SIP cannot work on its own for the purpose of hosting a VoIP call.

Download and Setup SIP-application

What Is The Best SIP App?

There are a range of different SIP apps available on the market, with providers such as Bria 5, Softphone Pro, Zoiper, and X-lite being some of the key players. But who is the best?


Acrobits is a lesser known SIP client, but has similar pricing to the Zoiper app. One major downside of this app is the exclusion of a desktop softphone option for PCs and Macs, which limits its business capabilities.

However, users pay a one-off fee of $6.99, and can enjoy useful features such as call recording, and the ability to be used with a range of different VoIP providers.

Bria Mobile

The Bria mobile app has won awards for its reasonable pricing ($0.99/per month or $9.99/ for a yearly subscription), it’s ability to switch easily between WIFI and mobile data, and it’s excellent customer service channels.


The pro version of the Zoiper app is priced at $4.99 in the iTunes stores, and is priced at $8.49 in the Google Play store. One major benefit of Zoiper is that it offers a free Lite version, enabling users to test out the software before they choose to go with the pro version.

Moreover, the in-app purchases are useful, since they enable the users to choose exactly what they want, rather than paying for features that they won’t necessarily use.

So which app is the best? Well, it largely depends on the features you’re looking for, and which ones you are prioritising for your business. However, for users just starting out with an SIP app for business, the Zoiper app appears to have the best initial offer, particularly since it provides a free trial.