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Click-to-Call Chrome Extension Development for a North American VoIP Services Provider

Click-to-Call Chrome Extension Development for a North American VoIP Services Provider

Frontend (JS, HTML, CSS)


The Customer is a provider of high-quality telecommunication services to individuals and businesses in North America. Sticking to geo-redundancy, the Customer ensures stable connection with over 200 countries worldwide. The Customer is ranked in the Deloitte Technology Fast 500 and Inc. 500 Fastest Growing Private Companies in America.


Wishing to improve its subscribers’ experience, the Customer turned to ScienceSoft to develop a Google Chrome extension enabling click-to-call. Additionally, the Customer requested that the extension be able to identify phone numbers in Windows, Mac and Linux desktop applications.


Based on its 11+ year expertise in telecommunication software development, ScienceSoft offered a solution that met the Customer’s requirements. ScienceSoft’s team developed the Google Chrome extension providing the following features:

  • Click-to-call – the extension initiates a call after a user clicks on a phone number on any Chrome tab or any other application using the URL-schemes ‘callto:’ and ‘tel:’.
  • Number highlighting – the extension makes an automatic search through every Chrome tab in order to find phone numbers and highlight them. Highlighted numbers are available for click-to-call.

The extension can be installed from the Chrome Web Store and utilized across all platforms supporting Chrome extensions (Windows, Mac and Linux).

Interaction with the Customer’s softswitch

The extension interacts with the Customer’s softswitch via an API. When a user initiates a click-to-call, the extension sends a request to the softswitch. Once the server identifies the extension’s ID, it generates a token serving as the unique user’s identifier. The generated token is used to make two more requests: the first one to extract a user’s phone numbers from the server, the second one to initiate a call by transmitting a source number and a destination number to the server.

At the final stage, the softswitch makes a simultaneous call to a user’s SIP phone and selected phone number.

Interaction with end users

The Customer’s subscribers upload the extension from the Chrome Web Store. When a user logs in, a dialer screen with a numeric keypad appears in the browser.

A user can select one of the phone numbers to be used as a source phone number for every call. If a user has several phone numbers, it’s possible to change the source number at any time via the settings page.

A user is able to input a contact number in two ways:

  • using click-to-call by choosing any number from the web page
  • using a keyboard to input a number manually

The extension recognizes both standard phone numbers and phonewords (phone numbers containing letters), which are automatically converted into a standard numeric format.

The extension is provided with a filter that crawls through every Chrome tab in order to find phone numbers and highlight/hyperlink them. Highlighted/hyperlinked numbers are available for click-to-call.

To let the extension identify phone numbers in Windows, Mac and Linux desktop applications, a subscriber should launch an installer that transforms the extension into a URL handler that identifies URL-schemes ‘callto:’ or ‘tel:’. This way, a user working with a Microsoft Word document sees all the phone numbers as hyperlinks and is able to initiate a call by clicking on the link.


The extension significantly facilitated phone call initiation. The Customer’s subscribers are now able to make instant calls via their browser or desktop applications. The extension is actively used among businesses as it ensures an uninterrupted working process and saves employees’ time.

The extension became the Customer’s new competitive advantage. The Customer reported a keen interest of its subscribers in the solution, as well as the increased number of outgoing calls made via the extension, which influenced positively the Customer’s average revenue per user (ARPU).

Technologies and Tools

Languages: HTML, CSS, JavaScript, jQuery, Objective-C.

Tools: Mac OS X Installation Package, NSIS.

Softswitch: Metaswitch.

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