15 Open-source Text To Speech TTS Libraries

Text-to-speech (TTS) technology has become increasingly popular, enabling computers and other devices to convert written text into spoken words. This technology benefits individuals with visual impairments and serves as a valuable tool for various applications such as language learning, audiobooks, virtual assistants, and more. One of the key factors driving its widespread adoption is the availability of open-source TTS libraries that provide developers with flexible solutions to implement this functionality into their projects.

In this blog post, we will explore 15 open-source TTS libraries that offer a range of features and options for developers looking to integrate text-to-speech capabilities into their applications or services. Whether you are an experienced developer or just starting your coding journey, these libraries can be excellent resources to enhance user experiences through speech synthesis.

1. Festival:

Festival is one of the oldest and most widely used open-source TTS systems. Developed by researchers at the University of Edinburgh’s Centre for Speech Technology Research (CSTR), it supports multiple languages and provides customizable voices using unit selection synthesis techniques.

2. eSpeak:

eSpeak is another popular choice among developers due to its simplicity and ease of use compared to many other TTS engines. It supports several languages, including English, Spanish, French, German, and more – making it versatile enough for global application development needs.

3. MaryTTS:

MaryTTS stands out from others due to its multilingual support and advanced features like prosody modification, which allows fine-grained control over speech output characteristics such as pitch contouring, speed variation, etc. Its modular architecture makes it highly extensible, allowing users to add custom components easily.

4. Rhasspy:

Rhasspy focuses on privacy-conscious voice assistant development by providing offline-only functionalities without relying on cloud-based APIs.This library uses Mozilla’s DeepSpeech ASR engine for speech recognition and supports various TTS engines like Flite, Picotts, etc., making it a comprehensive solution for building voice-controlled applications.

5. Mimic:

Mimic is an open-source TTS system developed by Mycroft AI to provide natural-sounding voices with minimal resources. It offers lightweight models suitable for embedded systems while maintaining high-quality output. The project also provides pre-trained English, Spanish, French, and German models.


PicoTTS is a small-footprint text-to-speech synthesis engine explicitly designed for resource-constrained devices such as mobile phones or IoT devices. Its compact size makes it ideal for applications where memory constraints are present without compromising the quality of synthesized speech.


OpenMary builds upon the MaryTTS platform but focuses on community-driven development and support. It allows users to contribute their language-specific modules and voices, which can be shared among other developers working with OpenMary.This collaborative approach ensures continuous improvement of available resources over time.

8. Festvox:

Festvox is part of Festival’s family of tools, providing a complete framework not only limited to TTS but also includes Automatic Speech Recognition (ASR) capabilities. Developers can create custom synthetic voices using Festvox’s Voice Building Framework(VBF), allowing them complete control over voice characteristics, such as pitch, tone, stress patterns, etc.

9. Flite:

Flite(pronounced “flight”) stands out due to its portability across different platforms ranging from smartphones to desktop computers to microcontrollers. Flite has been optimized, keeping low-latency requirements in mind, making it an ideal choice when real-time feedback/response is needed during interactive dialogues or gaming scenarios.


Sphinx4 differs from others mentioned here because instead of relying on cloud-based APIs, it runs entirely offline, enabling privacy-conscious application development. Users can choose between acoustic modeling approaches based on their requirements, and Sphinx4 supports multiple languages.

11. HTS:

HTS (HMM-based Speech Synthesis System) is a popular open-source TTS system that uses Hidden Markov Models(HMMs) to generate speech. It offers various synthesis techniques, including unit selection, HMM-based statistical parametric synthesis, and hybrid approaches. Users can build custom voices using the HTK toolkit bundled with the library.


Tacotron2 is an advanced neural network architecture developed by Google Research that has gained popularity due to its ability to produce high-quality, natural-sounding speech output. The model takes text as input and generates mel spectrograms, which are converted into audio waveforms using WaveGlow vocoder. This library requires powerful hardware resources but delivers state-of-the-art results in terms of voice quality.


DeepSpeech, also developed by Mozilla, is primarily known for its Automatic Speech Recognition(ASR) capabilities. However, it also includes built-in functionality for converting ASR outputs back into spoken words, making it a suitable choice when combined ASR-TTS applications must be implemented. Developers can fine-tune pre-trained models or train new ones from scratch based on specific needs.


SpeechSynthesizer is part of Microsoft’s Cognitive Services API, offering developers access to industry-leading TTS technology through simple RESTful APIs.It supports several programming languages, making it easy to integrate across different platforms. Microsoft’s Azure cloud platform powers this service, ensuring scalability, reliability, and global accessibility.

15. Acapela-Box:

Acapela-Box combines Acapela Group’s extensive expertise in voice technologies with a user-friendly web interface, enabling users to experiment with various parameters like pitch, tone, speed, etc. to create unique synthetic voices. Once satisfied, the generated voices can downloaded and used offline without any restrictions. Multiple language options available make Acapela-Box a versatile solution.


Open-source TTS libraries provide developers with various options to integrate text-to-speech capabilities into their applications or services. Whether you are looking for simplicity, multilingual support, privacy-conscious solutions, lightweight models for resource-constrained devices, or advanced neural network architectures, an open-source TTS library is available to meet your specific needs.

By leveraging these open-source resources and combining them with your creativity and expertise as a developer, you can enhance user experiences by providing natural-sounding speech synthesis in various languages across different platforms. With the continuous development and improvement of these libraries by dedicated communities, it’s exciting to see how this technology will evolve further. So go ahead, start exploring these open-source TTS libraries, and unlock new possibilities for voice-enabled applications!

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