Cartesia builds the fastest, most natural speech AI — text-to-speech, transcription, and a complete platform for shipping enterprise voice agents. One API, no tradeoffs.
Ranked #1 for naturalness. Sub-90ms latency. Natively multilingual in 40+ languages. Sonic understands emotional subtext and delivers it — automatically.
Fastest streaming TTS on the market. Built for real-time voice agents where latency is everything.
Natively multilingual, not translated. Natural intonation in every language.
Sonic reads emotional subtext from your prompts and adds laughter, excitement, or calm without any extra markup.
Clone any voice and deploy it across all supported languages instantly.
The fastest and most accurate streaming transcription model. Built for live voice agents where every millisecond of latency matters.
Each word appears as it's spoken — zero buffering, no batch delays.
Trained on diverse accents and noisy environments. Works in the real world.
Native integration means zero-copy latency when used in the Cartesia stack.
Line is the complete platform for voice agents — powered by Sonic and Ink, with built-in telephony, session management, and analytics.
Sonic TTS + Ink STT natively integrated — lowest possible round-trip latency.
SIP trunking, PSTN, WebRTC. Deploy to phone numbers in minutes.
Session replays, latency breakdowns, transcript search, and custom dashboards.
State Space Models — a fundamentally new AI primitive invented at Stanford AI Lab. Lower latency, longer context, more efficient than transformers.
A new primitive for AI, invented at Stanford AI Lab. Lower latency, longer context, and more efficient than transformers — purpose-built for streaming audio.
SSMs process audio streams token-by-token, enabling sub-90ms response times that are simply impossible with traditional transformer architectures.
Our founding team invented SSMs during their PhDs at Stanford AI Lab and published the foundational papers. This isn't applied research — it's the source.
Cartesia's Sonic model is the only TTS we've found that's fast enough for real production voice agents. The latency is genuinely a category apart.
Whether you're building an AI agent, enterprise telephony, or a next-gen product — we'll help you ship faster.
State Space Models (SSMs) are a new class of neural network architecture invented by Cartesia's founding team during their PhDs at Stanford AI Lab. Unlike transformers, SSMs process sequences with linear rather than quadratic complexity — making them dramatically faster and more efficient for streaming audio tasks. Cartesia's Mamba architecture is the seminal SSM work, and our models are the first to make SSMs practical for real-time speech AI at scale.
Sonic is ranked #1 for naturalness in independent evaluations and offers sub-90ms latency — significantly faster than ElevenLabs or OpenAI TTS. For real-time voice agents where conversational latency is critical, Sonic's SSM architecture provides a structural latency advantage that transformer-based models simply cannot match. Sonic also supports automatic emotion and laughter without any markup, and voice cloning across all 40+ supported languages.
Yes. Sonic supports voice cloning with a short audio sample. Cloned voices work natively across all 40+ supported languages — so you can clone an English speaker and deploy them speaking perfect Japanese, French, or Portuguese without any additional training. Voice clones are available on all paid plans and via API.
Sonic supports 40+ languages natively — not via translation, but with native-speaker-quality intonation and pronunciation in each language. Supported languages include English, French, German, Japanese, Spanish, Portuguese, Chinese, Korean, Italian, Dutch, Russian, Polish, Turkish, Arabic, Hindi, and many more. All languages are available via the same API endpoint.
Getting started is free. Sign up at cartesia.ai to get API keys immediately — no credit card required. Our REST API and Python/TypeScript SDKs let you stream TTS audio in fewer than 10 lines of code. For enterprise voice agent use cases, reach out to Karan@cartesia.cloud and we'll set up a dedicated onboarding call with a solutions engineer.