The Best Open Source, AI, and Free Speech-to-Text Engines

May 20, 2023

Speech-to-Text (STT) technology has seen remarkable advancements in recent years, transforming the way we interact with technology and making audio and video content more accessible. Several open-source and AI-powered solutions have emerged, offering accurate and reliable speech-to-text transcription. In this article, we'll explore some of the best open-source, AI-driven, and free speech-to-text engines available today.

1. Mozilla DeepSpeech

DeepSpeech, developed by Mozilla, is an open-source, AI-based speech recognition engine. It is built on deep learning frameworks, leveraging recurrent neural networks (RNN) and the TensorFlow library. DeepSpeech offers impressive accuracy and is continually improved through community contributions. As an open-source project, DeepSpeech is accessible to developers and researchers, allowing them to fine-tune the engine for specific use cases.

Website: Mozilla DeepSpeech

2. Kaldi

Kaldi is a widely used open-source toolkit for speech recognition. While it requires more expertise to set up and use compared to some other solutions, Kaldi is highly flexible and customizable. It is particularly popular in academic and research settings, and it provides state-of-the-art speech recognition capabilities.

Website: Kaldi Speech Recognition Toolkit

3. CMU Sphinx

CMU Sphinx, also known as PocketSphinx, is a time-tested open-source speech recognition system developed by Carnegie Mellon University. It offers a lightweight and efficient solution for both offline and online speech recognition applications. CMU Sphinx is well-suited for resource-constrained devices and applications that require real-time processing.

Website: CMU Sphinx

4., now owned by Facebook, is an AI-driven platform that provides natural language processing and speech recognition capabilities. It offers an easy-to-use API, making it a great choice for developers looking to integrate speech-to-text functionality into their applications rapidly. provides pre-trained models and the ability to train custom models for domain-specific needs.


5. Google Cloud Speech-to-Text

Google Cloud Speech-to-Text is a powerful cloud-based speech recognition service offered by Google. While it is not open-source, Google provides a free tier with limited usage for developers to try the service. It excels in accuracy and supports a wide range of languages and audio formats. Google's vast infrastructure ensures scalability and reliability, making it suitable for enterprise-level applications.

Website: Google Cloud Speech-to-Text

6. IBM Watson Speech to Text

IBM Watson Speech to Text is another cloud-based speech recognition service with robust features. It offers real-time and batch processing options and supports multiple languages. IBM Watson's AI capabilities enable it to handle noisy environments and various accents effectively. Like Google Cloud Speech-to-Text, it also offers a free trial for developers to explore its capabilities.

Website: IBM Watson Speech to Text


Choosing the right speech-to-text engine depends on your specific requirements, such as accuracy, customization options, and scalability. Open-source solutions like Mozilla DeepSpeech and Kaldi offer flexibility and customization for research and development purposes. On the other hand, cloud-based services like Google Cloud Speech-to-Text and IBM Watson Speech to Text provide ease of integration and reliability for production-level applications.

Whether you prefer an open-source solution or a cloud-based service, the availability of advanced speech-to-text engines has democratized access to this technology, empowering developers to create innovative applications that leverage the power of speech recognition.