Best open-source alternatives to Twilio

Novu is an open-source notification infrastructure project aimed at developers building modern products. It centralizes notification delivery across channels such as inbox/in-app, email, SMS, push, and chat, so teams can manage messaging logic through one platform instead of integrating each provider separately. The project combines a unified API with an admin panel and embeddable UI components. It is designed to let applications add a real-time notification center and user preferences UI quickly, while also supporting workflows, channel conditions, and provider management through the Novu interface and SDKs.

Fonoster is a programmable telecommunications platform positioned as an open-source alternative to Twilio. It is aimed at businesses and developers that need to build voice-driven applications, automate call flows, and expose telephony capabilities through an API-first stack. The README shows that the project supports multitenant deployments, role-based access control, OAuth2 and JWT authentication, and integrations such as S3 and Google Speech APIs. Developers can build voice applications using the provided SDKs and voice verbs, then deploy them as services that handle call control, speech, DTMF gathering, recording, and call routing. The project also provides guidance for self-hosting with Docker and points users to its documentation for quickstart and deployment instructions.