Top 7 open source chatbots builder

The race to automate human-to-machine conversations has never been more exciting. In a world dominated by AI tools, developers are looking for open-source chatbot builders that offer freedom, flexibility, and full control over data and logic.

But which frameworks truly stand out in 2025? This article breaks down the top 7 open-source chatbot builders that are redefining how developers create intelligent, conversational AI across platforms like WhatsApp, Slack, websites, and mobile apps.

Why Open-Source Chatbot Builders Matter More Than Ever

Closed chatbot platforms limit your creativity and tie your data to third-party servers. For developers who want custom logic, privacy control, and seamless backend integration, open-source solutions offer:

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Code Transparency
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Unlimited Customization
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Cost Efficiency
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Strong Developer Communities

Whether you're building a multilingual customer support bot or integrating chat logic into internal tools, these frameworks give you the foundation and freedom to scale.

Feature Comparison Table

Name Language NLP Engine UI Editor Best For
Rasa Python Built-in ❌ Complex NLP bots
Botpress Node.js Built-in/External ✅ GUI + Code builders
MS Bot Framework .NET/Node Azure LUIS ❌ Enterprise integrations
ChatterBot Python ML-based ❌ Beginners, small bots
DeepPavlov Python BERT, NLP models ❌ Research, QA systems
Alan AI JS/Kotlin Voice SDK ✅ Voice-based assistants
Tock Kotlin/Java Built-in ✅ Multilingual, Europe

🧠 1. Rasa — The NLP Powerhouse (Python)

“Open-source machine learning framework to automate text and voice-based conversations.”
  • Language: Python
  • NLP Engine: Built-in with customizable pipelines
  • Best For: Complex bots, enterprise NLP needs
  • License: Apache 2.0

Why Developers Love It:

Rasa combines NLU and dialogue management under one hood. It lets you build custom conversational flows using stories, actions, and intents. With integrations for Slack, Twilio, Facebook Messenger, and more, Rasa is enterprise-grade without the price tag.

➡️ Read the Rasa docs

🧩 2. Botpress — The Modular Visual Builder (Node.js)

“The WordPress of chatbot builders.”
  • Language: Node.js
  • NLP: Built-in or connect to external services
  • Best For: Developers who want GUI + code
  • License: AGPLv3

Key Highlights:

Botpress offers a drag-and-drop interface backed by powerful code logic. Its modular architecture and REST API make it perfect for developers looking to balance visual design and custom backend logic.

🔗 Try Botpress Cloud or Self-hosted