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AI Voice Generators

Cartesia

A developer-focused voice AI platform built for real-time conversational applications, offering ultra-low-latency text-to-speech, speech-to-text, and end-to-end voice agent infrastructure.

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What it does

Cartesia is a developer-focused voice AI platform built around real-time conversational applications rather than content production. Its Sonic text-to-speech model is optimized for extremely low latency, which is the deciding factor in whether a voice agent feels natural to talk to, and it pairs Sonic with Ink, a speech-to-text model, and Line, a managed voice-agent product that handles the full conversational loop.

Unlike studio-style tools built for producing finished videos or podcasts, Cartesia is consumed almost entirely through an API and SDKs, making it a fit for engineering teams building voice agents, IVR systems, or voice-enabled apps rather than marketers producing narrated content by hand.

Ideal users

  • Developers building voice agents, IVRs, or conversational AI products that need sub-100ms response latency
  • Teams that want a combined text-to-speech, speech-to-text, and voice-agent stack rather than stitching together separate services
  • Startups building on Cartesia's Sonic (TTS), Ink (STT), and Line (voice agent) products

Who should avoid it

  • You need a no-code editor for producing narrated videos — Murf AI or WellSaid Labs are built for that instead
  • You just want to listen to articles or PDFs as a consumer — Speechify is designed for that use case

Key features

  • Sonic text-to-speech model with time-to-first-audio reported as low as roughly 40-90ms
  • Ink speech-to-text model for transcribing user speech in real time
  • Line, a managed voice-agent product that combines TTS, STT, and turn-taking logic
  • Instant and professional voice cloning
  • Credit-based, usage-driven API pricing with a functional free developer tier

Pros

  • Among the lowest-latency voice APIs available, which matters directly for how natural a voice agent feels in conversation
  • Offers TTS, STT, and voice-agent orchestration as one connected stack instead of assembling separate vendors
  • Transparent, usage-based pricing with a free tier suitable for prototyping

Cons

  • Developer/API-first product — there is no timeline video editor or non-technical studio interface like Murf or WellSaid offer
  • Newer entrant than ElevenLabs, so its voice library and language coverage are comparatively smaller — Cartesia's Sonic model officially supports 42 languages, and while Cartesia does not publish an exact total voice count, its voice library is smaller than ElevenLabs' larger, longer-established catalog
  • Credit costs can add up quickly for high-volume, always-on voice agents

Pricing

Free — $5/month (Pro plan)

Free: $0/month, 20K credits (about 27 TTS minutes), 1 agent slot. Pro: $5/month, 100K credits, adds commercial license and instant voice cloning. Startup: $49/month, 1.25M credits, adds professional voice cloning. Scale: $299/month, 8M credits, priority support and higher concurrency. Enterprise: custom pricing with DPAs, BAAs, and SSO. Voice agent call time is billed separately at $0.06 per minute across all tiers, plus $0.014 per minute for telephony when using a Cartesia-provided phone number; confirm current figures at cartesia.ai/pricing since usage-based pricing can change.

Typical workflows

  • A developer integrates Cartesia's Sonic API into a customer-support voice agent so responses are spoken back with minimal delay after the LLM generates text.
  • A startup uses Cartesia's Ink model to transcribe live customer calls, then feeds the transcript to an LLM and speaks the reply back through Sonic, all within Cartesia's stack.
  • A product team prototypes a voice assistant on the free tier before moving to a paid plan once usage grows.

Integrations

  • REST and WebSocket streaming API with SDKs for common languages
  • Commonly used alongside voice-agent orchestration frameworks such as LiveKit Agents, Rasa (Cartesia is Rasa's default voice provider), and Bolna

Privacy & security notes

Cartesia states that customer content may be used to train and improve its models by default, though customers can opt out of future training use via a request form; enterprise customers can also enable a Zero Data Retention setting that disables storage, logging, and training entirely. Cartesia's infrastructure holds SOC 2 Type II, HIPAA, PCI-DSS, and GDPR compliance, per its own legal and trust pages (cartesia.ai/legal, trust.cartesia.ai).

Frequently asked questions

What makes Cartesia different from ElevenLabs?

Both offer high-quality text-to-speech and voice cloning, but Cartesia is built specifically around ultra-low latency and a combined TTS, STT, and voice-agent stack for real-time conversational applications, while ElevenLabs offers a broader content-creation toolset — dubbing, sound effects, and a larger established voice library — alongside its API.

Do I need to be a developer to use Cartesia?

Largely yes. Cartesia is API/SDK-first and aimed at teams building voice-enabled products, not a drag-and-drop studio for producing narrated videos.

Can Cartesia power a full voice agent, or just generate speech?

Its Line product is designed to handle the full voice-agent loop — speech-to-text, turn-taking, and text-to-speech — not just raw text-to-speech generation.

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