Cartesia
Cartesia is a real-time speech platform that combines Sonic text-to-speech, Ink speech-to-text and managed voice agents behind one API. It is mainly used to build live phone agents and to generate spoken audio for products and content.
#29 in Video & Audio ToolsText to Speech & AI VoiceFree plan
Who it's for
Best for
Developers building live phone agents where response delay ruins the call
Teams piping speech output into existing agent or automation workflows
Not for
- Developers needing custom pronunciation dictionaries for non-English speech
Cost-sensitive builders running heavy speech-to-text volume
Free plan$0
Pro$5/mo
Startup$49/mo
Scale$299/mo
Features
Sonic text to speech
Sonic is the text-to-speech model, described as ultra-realistic voice synthesis built for low latency at scale.
Ink speech to text
Ink is the streaming transcription model, positioned as the fastest and most accurate option in the lineup.
Managed Agents
Managed Agents is a platform for building and shipping enterprise voice agents, running on the same speech models.
Cloud, on-premise and on-device
Models and agents deploy across cloud, on-premise and on-device, with inference kept in-region for latency and data residency requirements.
State space model research
The research team created state space models such as Mamba and H-Nets, which underlie the real-time speech stack.
What users say
Pros
- Latency is treated as a priority and streaming as a core use case, so the model targets live conversational agents.
- A working setup pipes OpenTelemetry events through FastAPI and Gemini into Cartesia for spoken agent completion summaries.
Cons
- Non-English pronunciation dictionaries fail: Dutch text is read using English rules, so custom pronunciations never apply.
- Transcription pricing feels steep, prompting a hunt for rival speech-to-text models.
A selection of the review sources we used:
Summarized from public user reviews and community discussions. View details
Global Traffic Rank
Top 100k
Alternatives
Rank#29 in category#6 in category#17 in category#24 in category
Free planYesYesYesYes
ProStreaming-first design, working agent pipelinesMost natural voices, top-rated transcription, cheap for hobby useEasy-listening long reads, lifelike clones, runs on home GPUsNatural voices, cheaper than audiobooks, textbook listening
Better forGenerating expressive multi-speaker dialogue with emotion tags and prompt-based voice designRunning open-weight voice models locally on consumer GPUs, directed by line-by-line emotion tagsReading PDFs, documents, and web pages aloud with synchronized highlighting across browser and mobile apps
Weaker atRunning high-volume phone agents without steep per-character credit costsGenerating consistent, stable voice takes on the first try without tone shifts or voice breaksBuilding low-latency streaming audio pipelines for live conversational voice agents