What is Fonoster used for?

Fonoster is an open-source programmable telecommunications stack, positioned as an alternative to Twilio, for building voice applications, PBX features and cloud telephony. It is a good fit for building IVR and voice bots, replacing Twilio with a self-hosted stack, and adding telephony to business applications.

Is Fonoster open source?

Yes. Fonoster is open source under the MIT licence. Its source code is on GitHub at fonoster/fonoster and is written mainly in TypeScript.

Yes. Fonoster is open source, so the software itself is free to use.

Can I self-host Fonoster?

Yes. Fonoster can be self-hosted on your own server or infrastructure.

What is Fonoster an alternative to?

Fonoster is an open-source alternative to Twilio, Vonage API, Sinch and Plivo. Other open-source alternatives to Twilio include LiveKit, FreeSWITCH and OpenWA.

Is Fonoster actively maintained?

Yes. The most recent commit to Fonoster was on 18 September 2026, and the latest release is v0.22.14, published on 11 September 2026. The project has 8.1k stars on GitHub.

Fonoster: open-source alternative to Twilio, Vonage API

About Fonoster

Fonoster is an open-source cloud communications platform presented as an alternative to Twilio. Its stated aim is a programmable telecommunications stack that lets businesses connect telephony services with the internet through a cloud-based utility, and the topics mention VoIP, WebRTC, UCaaS and CPaaS.

Main features include multitenancy, easy deployment of PBX functionality, programmable voice applications, a Node.js SDK, support for Amazon S3, secured API endpoints with Let's Encrypt, OAuth2 and JWT authentication, role-based access control, a plugin-based CLI and Google speech APIs. A voice application is a server process that drives a call using verbs such as Answer, Hangup, Play, Say, Gather, Stream, Dial, Record, Mute and Unmute, and everything in Fonoster is API first, including starting a call with the SDK.

Fonoster is written in TypeScript on Node.js and designed for Kubernetes deployments. It is licensed under MIT and aimed at developers and companies building voice bots, IVR systems and cloud phone features that they can run on their own infrastructure.

Key features

Programmable voice applications
PBX functionality deployment
SDK for Node.js developers
Multitenancy with role-based access control
OAuth2 and JWT authentication
Speech recognition and synthesis hooks
Plugin-based command-line tool

Good fit for

→Building IVR and voice bots
→Replacing Twilio with a self-hosted stack
→Adding telephony to business applications

Built with: TypeScript; Kubernetes; JavaScript; Node.js
Tags: voip; telephony; cpaas; twilio-alternative; programmable-voice; webrtc; pbx; typescript; kubernetes

Fonoster: questions and answers

What is Fonoster used for?: Fonoster is an open-source programmable telecommunications stack, positioned as an alternative to Twilio, for building voice applications, PBX features and cloud telephony. It is a good fit for building IVR and voice bots, replacing Twilio with a self-hosted stack, and adding telephony to business applications.
Is Fonoster open source?: Yes. Fonoster is open source under the MIT licence. Its source code is on GitHub at fonoster/fonoster and is written mainly in TypeScript.
Is Fonoster free?: Yes. Fonoster is open source, so the software itself is free to use.
Can I self-host Fonoster?: Yes. Fonoster can be self-hosted on your own server or infrastructure.
What is Fonoster an alternative to?: Fonoster is an open-source alternative to Twilio, Vonage API, Sinch and Plivo. Other open-source alternatives to Twilio include LiveKit, FreeSWITCH and OpenWA.
Is Fonoster actively maintained?: Yes. The most recent commit to Fonoster was on 18 September 2026, and the latest release is v0.22.14, published on 11 September 2026. The project has 8.1k stars on GitHub.