Comparison of speech synthesizers

Here is a non-exhaustive comparison of speech synthesis programs:

General

Name Creator(s) First public release date Latest stable version Software license
15.ai 15 2020 2022
Apple PlainTalk Apple Inc. 1984 2018 Bundled with Mac OS X
AT&T Natural Voices AT&T Natural Voices ? 2008 Proprietary
Polly Amazon AWS 2016 2019 Proprietary
Cepstral Cepstral 2000 2013 Proprietary
CereProc CereProc 2006 2017, February Proprietary
eSpeak Jonathan Duddington 2006, February 10 2022, April 3 GPLv3+
Festival Speech Synthesis System CSTR ? 2014, December MIT-like license
FreeTTS Paul Lamere
Philip Kwok
Dirk Schnelle-Walka
Willie Walker
... 		2001, December 14 2009, March 9 BSD
LumenVox LumenVox 2011 2019 Proprietary
Microsoft Speech API Microsoft 1995 2012 Bundled with Windows
VoiceText ReadSpeaker (Formerly Neospeech) 2002 2017 Proprietary
Nuance Vocalizer Nuance Communications, Inc. ? 2018 Proprietary

Technical voice details

Platform SSML SAPI version WS PLS CLI
15.ai ? ? ? ? ?
Apple PlainTalk ? ? ? ? ?
AT&T Natural Voices Yes 5.1 ? ? ?
Cepstral (company) Yes 5.x Yes Yes Yes
CereProc Yes 5.x Yes Yes Yes
eSpeak Yes 5.x ? ? Yes
Festival Speech Synthesis System ? ? ? ? Yes
FreeTTS ? ? ? ? ?
LumenVox Yes 5.x Yes Yes Yes
Microsoft Speech API 5.x only 4.x/5.x ? ? ?
Nuance Vocalizer ? ? ? ? ?
VoiceText Yes 5.x ? ? ?

Technical details

Name Online demo Available language(s) Available voices Programming language Operating system(s)
15.ai Yes English (United States) 50+ Python Any
Apple PlainTalk ? English (United States), ... 15+ ? Macintosh
AT&T Natural Voices Yes English (British), English (Indian), English (US), French, French (Canadian), German, Italian, Spanish (Latin American) 20 C++ Linux
Windows
Cepstral Yes English (British), English (US), Italian, French (Canadian), German, Spanish (American), ... 25+ C/C++ Mac OS X
Windows
i386-Linux
x86-64-Linux
Sparc-Solaris
i386-Solaris
CereProc Yes English (British), English (US), English (Scottish), English (Irish), French, French (Canadian), German, Austrian German, Italian, Irish, Spanish (Castilian), Spanish (Latin American), Dutch, Polish, Portuguese, Portuguese (Brazilian), Japanese, Catalan, Scottish Gaelic, Swedish, Russian, Mandarin 46

Java / C C++ / Objective C / Python / C# & .Net through SAPI

Linux
Windows
Mac OS X
Embedded Linux
Android
iOS
Cloud service
eSpeak Samples Afrikaans, Albanian, Armenian, Cantonese, Catalan, Croatian, Czech, Danish, Dutch, English (British, US, Scottish, Westindies...), Esperanto, Estonian, Finnish, French (France, Belgium), Georgian, German, Greek, Hindi, Hungarian, Icelandic, Indonesian, Italian, Kannada, Kurdish, Latvian, Lojban, Macedonian, Malayalam, Mandarin, Norwegian, Persian, Polish, Portuguese, Romanian, Russian, Serbian, Slovak, Spanish, Swahili, Swedish, Tamil, Turkish, Vietnamese, Welsh. several C++ Linux
Windows
Mac OS X
RISC OS
Festival Speech Synthesis System Yes English (UK), English (US), Spanish, Hindi, Croatian, Finnish, Polish, Welsh. Several C++ Linux
Windows
FreeTTS ? English... Several Java Cross-platform
LumenVox Yes Danish, Dutch, English (Australian), English (US), English (UK), English (Welsh), English (Indian), French, French (Canadian), German, Icelandic, Italian, Polish, Portuguese, Portuguese (Brazilian), Romanian, Russian, Spanish (North American), Spanish (Latin American), Spanish (Castilian), Swedish, Turkish, Welsh, Welsh English 57 C/C++ Windows
Linux
Nuance Vocalizer Yes US English, Australian English, Indian English, Irish English, South African English, UK English, Argentinian Spanish, Castilian Spanish, Colombian Spanish, Mexican Spanish, Arabic, Catalan, Basque, Galician, Dutch, Belgian Dutch, Portuguese, Brazilian Portuguese, Bulgarian, French, Canadian French, Cantonese (Hong Kong), Mandarin, Mandarin Taiwanese, Czech, Danish, Finnish, German, Greek, Hebrew, Hindi, Hungarian, Indonesian, Italian, Japanese, Korean, Norwegian, Polish, Romanian, Russian, Slovak, Swedish, Thai, Turkish 70+ C/C++ Windows
Linux
Android
VoiceText Yes English (US), English (British), American Spanish, Canadian French, Chinese Mandarin, Japanese, Korean 13 C/C++/Java Windows
Linux