Cartesia
Cartesia is a voice-AI company whose models are built for real-time conversation, where the delay before the first sound matters more than anything else. It was founded in 2023 by Karan Goel (CEO), Albert Gu, Arjun Desai and Brandon Yang, who met as PhD students in Christopher Ré's group at the Stanford AI Lab, with Ré as a co-founder and advisor. That group's research on state space models (SSMs), an alternative to the transformer with lower latency and longer memory, is the technical bet behind the company. Cartesia raised a $27 million seed round led by Index Ventures in December 2024 and a $64 million Series A led by Kleiner Perkins in March 2025.
Products (October 2026)
| Product | What it does | Latest release |
|---|---|---|
| Sonic | Streaming text-to-speech in 44 languages and 61 locales, with about 60 emotion values, a [laughter] tag and speed and volume controls | Sonic-3.6, GA August 27, 2026 (the line began in May 2024) |
| Ink | Streaming speech-to-text for agents, with turn events and "semantic endpointing"; five languages | Ink-2, July 9, 2026 |
| Line | A code-first platform for building voice agents: any LLM, SIP (beta), Twilio, batch calling and evaluations | Launched August 19, 2025 |
| Voice cloning and Voice Changer | Instant clones from about 10 seconds of audio; professional clones on higher plans; voice-to-voice conversion | Professional cloning May 2025 |
Cartesia markets Sonic-3.6 on first audio in under 90 milliseconds. It says listeners preferred it in up to 93% of blind head-to-head tests across fifteen locales, and it claimed first place on Artificial Analysis's speech arena at launch. These are vendor claims, and ElevenLabs claimed the same arena's top spot a month later for Eleven v4. Rankings move with every release.
Pricing and Deployment
Cartesia sells monthly credit plans. Free (20,000 credits, no commercial use) is followed by Pro at $5, Startup at $49 and Scale at $299 a month, with speech at one credit per character. At list prices its plans include more characters per dollar than ElevenLabs': the $299 Scale plan carries 8 million credits. Its deployment options are broad. Sonic can run in a customer's own cloud through Baseten, Amazon SageMaker or Together AI, self-hosted Sonic-3.6 became available to enterprise customers in September 2026, and Line offers zero data retention on enterprise plans. That suits call centers and regulated industries that can't send audio to a shared API.
How It Compares
Cartesia is a specialist. ElevenLabs is far broader, covering narration, transcription, dubbing, music and cleanup under one account, and it's the usual choice for produced audio and AI dubbing. Cartesia is the usual choice where speech has to feel immediate: phone agents, assistants and other conversational AI. Deepgram now competes on both ends of a voice agent with Flux recognition and Flux TTS. Open-weight text-to-speech models compete for teams that want to host their own. Easy cloning from a short sample brings the same voice-deepfake risk at every vendor, so a consent record for each cloned voice is good practice. For the head-to-head, see ElevenLabs vs Cartesia.
Further Reading
- Sonic-3.6 — Cartesia; the August 2026 release, latency and deployment options
- Ink-2 — Cartesia; the July 2026 speech-to-text model
- Cartesia changelog (2026) — Sonic-3.6 GA, self-hosting and Line updates
- Cartesia pricing — plans and credits
- Cartesia blog — seed and Series A announcements and model launches