Flite
Flite is a small, fast, open-source run-time text-to-speech engine that converts strings or files into spoken audio.
What Flite is
Flite is a small, fast, open-source run-time text-to-speech engine that converts strings or files into spoken audio. Its command-line program can send synthesized output to audio devices or waveform files, including WAV, while the library exposes functions for embedding speech in applications. Written in ANSI C, it compiles and runs without Festival or FestVox. The project targets small devices such as phones and PDAs as well as servers serving many ports. The distribution includes one 8K diphone voice, a pruned lexicon, and US English models; additional voices may be loaded from files, downloaded, or retrieved over HTTP. Flite describes Indic support and grapheme support for hundreds of languages. Voice and language data can be compiled into C or loaded at runtime. The README describes thread safety after initialization and SAPI support for clustergen voices. The bundled voice uses fewer resources but is more robotic than other Flite voice technology. Core code is free for commercial products under BSD-like terms, while some files have separate licenses.
Good
- ANSI C engine runs without Festival or FestVox
- Command line and library interfaces
- Additional voices can load from files or HTTP
- Supports WAV waveform output
- Commercial use permitted for core code
Watch out
- Bundled voice is an 8K sample voice
- The included voice sounds more robotic
- Some included files have separate licenses
- Debug feature options can stop operation
Who it suits
Flite suits developers embedding speech synthesis in Android, Linux, macOS, Windows, self-hosted, or API-based projects. It is useful where low resource use, WAV output, or commercial source-code licensing matters.
Verdict
Flite offers an embeddable speech engine across several platforms, with runtime voice loading and modest resource needs. Its included voice favors efficiency over naturalness, so voice selection matters for deployments.
Plans and prices
From Flite's own pricing page, checked 12 Oct 2026.
| Plan | Price | What it gives you |
|---|---|---|
| Flite | Free | Open source speech synthesis engine · single 8K diphone voice included |
The facts
Each one read from Flite's own pages, with the date it was checked.
What it does
- API access
- Yeschecked 20 Sep 2026
- Commercial use
- Yeschecked 20 Sep 2026
- Deployment
- Voice, lexicon, and language data can be compiled into C representations and linked into an application, and voice files may also be loaded from disk or HTTP.checked 12 Oct 2026
- Export formats
- WAVchecked 20 Sep 2026
- Features
- The command-line program synthesizes strings or files to audio devices or waveform files, and the library provides simple functions for applications.checked 12 Oct 2026
- Implementation
- The engine is written in ANSI C and does not require Festival or FestVox to compile or run.checked 12 Oct 2026
- Integration
- Flite can be used as a library in applications, and the repository documents SAPI support for clustergen voices.checked 12 Oct 2026
- Languages
- The project describes Indic language support and hundreds of languages through grapheme support.checked 12 Oct 2026
- License
- The project says the core code is free to use in commercial products under its BSD-like copyright terms; some included files have separate licenses.checked 12 Oct 2026
- Purpose
- Flite is a small, fast, open source run-time text-to-speech engine.checked 12 Oct 2026
- Quality tradeoff
- The bundled 8 kHz diphone voice is described as a sample voice, and the README notes it is less computationally expensive but more robotic than other voice technology in Flite.checked 12 Oct 2026
- Resource limits
- For standard diphone voices, the README estimates maximum run-time memory at less than twice the memory needed for the generated waveform, or under 1 MB on 32-bit architectures.checked 12 Oct 2026
- Security
- The README warns that command-line feature-setting options are debug facilities and malicious values can stop Flite from working, so they are not intended for standard users.checked 12 Oct 2026
- Thread safety
- The README describes Flite as thread safe, with the release notes specifying thread safety after initialization.checked 12 Oct 2026
- Use cases
- It is designed for small devices such as phones and PDAs, as well as large servers that need to serve many ports.checked 12 Oct 2026
- Voices
- The distribution includes one 8K diphone voice, a pruned lexicon, and US English models; additional voices can be downloaded or loaded from files or an HTTP connection.checked 12 Oct 2026
Where it runs
- Companion app
- The README describes Bard Storyteller as an app that reads text, HTML, and EPUB ebooks aloud using Flite.checked 12 Oct 2026
- Platforms
- The project reports successful builds on Linux, Mac OS X, Android, FreeBSD, Solaris, Windows through Cygwin or Windows Subsystem for Linux, and experimental WASI.checked 12 Oct 2026
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