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Fonoster: The open-source alternative to Twilio

Fonoster Inc researches an innovative Programmable Telecommunications Stack that will allow for an entirely cloud-based utility for businesses to connect telephony services with the Internet.

Fonoster - Engage with your customers with VoIP or SMS | Product Hunt

build license: MIT Tweet


The most notable features on FN 0.2 are:

  • Cloud initialization with Cloud-Init
  • Multitenancy
  • Easy deployment of PBXs functionalities
  • Programmable Voice Applications
  • NodeJS SDK
  • Web SDK
  • Support for Amazon Simple Storage Service (S3)
  • Secure API endpoints with Let's Encrypt
  • Authentication with OAuth2
  • Authentication with JWT
  • Role-Based Access Control (RBAC)
  • Plugins-based Command-line Tool
  • Support for Google Speech API
  • Experimental support for Cloud Functions
  • Experimental support for Secret management

Code Examples

A Voice Application is a server that takes control of the flow in a call. A Voice Application can use any combination of the following verbs:

  • Answer - Accepts an incoming call
  • Hangup - Closes the call
  • Play - Takes an URL or file and streams the sound back to the calling party
  • Say - Takes a text, synthesizes the text into audio, and streams back the result
  • Gather - Waits for DTMF or speech events and returns back the result
  • SGather - Returns a stream for future DTMF and speech results
  • Dial - Passes the call to an Agent or a Number at the PSTN
  • Record - It records the voice of the calling party and saves the audio on the Storage sub-system
  • Mute - It tells the channel to stop sending media, effectively muting the channel
  • Unmute - It tells the channel to allow media flow

Voice Application Example:

const { VoiceServer } = require("@fonoster/voice");
const voiceServer = new VoiceServer({ base: '/voiceapp' });

voiceServer.listen((req, res) => {

// your app will be at 
// and you can easily publish it to the Internet with:
// ngrok http 3000

Everything in FN is an API first, and initiating a call is no exception. You can use the SDK to start a call with a few lines of code.

Example of originating a call with the SDK:

const Fonoster = require("@fonoster/sdk");
const callManager = new Fonoster.CallManager();{
 from: "9842753574",
 to: "17853178070",
 webhook: ""

Getting Started

To get started with FN use the following resources:

Give a Star! ⭐

If you like this project or plan to use it in the future, please give it a star. Thanks πŸ™

Bugs and Feedback

For bugs, questions, and discussions, please use the Github Issues


For contributing, please see the following links:

We're glad to be supported by respected companies and individuals from several industries. See our Github Sponsors learn more.


Find all supporters in our file.

Become a Github Sponsor

Special Announcement:

We now have a Slack Channel
There we plan to discuss roadmaps, feature requests and more
Join the channel



Copyright (C) 2022 by Fonoster Inc. MIT License (see LICENSE for details).