Fonoster
An open-source programmable telecommunications stack, positioned as an alternative to Twilio, for building voice applications, PBX features and cloud telephony.
- GitHub stars
- 8.1k
- Last commit
- 15 days ago
- Latest release
- v0.22.14
- Licence
- MIT
- Self-hosted
- Yes

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
Pricing: Free and open source under the MIT licence.