Cartesia

What it's good for

• 1

  Real-time phone and voice agents where latency makes or breaks the experience

• 2

  Live dubbing and narration that has to keep pace with audio or video

• 3

  Building a full voice-agent stack (TTS, STT, orchestration) on one platform with Line

• 4

  Multilingual voice features across 40-plus languages

• 5

  Adding fast, natural speech to a product without standing up your own audio infra

Pricing

• Free

  Trial limits to evaluate

  Free

• Pro

  Annual billing, higher limits

  $4/mo

• Premium models

  Top-quality voice generation

  $35/M chars

How to use it

Prototype against the free tier to hear the latency for yourself, the 90ms first byte is the thing to feel, not just read about. Use Sonic for speech out and Ink for speech in; reach for Line when you are building a full voice agent rather than wiring the pieces yourself. Meter premium-model usage by characters, since that is where cost accrues. If you need a huge voice-cloning catalog more than raw speed, compare against ElevenLabs.

Pros & cons

Frequently asked questions

• Is Cartesia free?

  Yes, there is a free tier with trial limits to evaluate it, plus Pro at $4 a month on annual billing for higher limits. Premium models run about $35 per million characters, so heavy generation is metered by characters. Prototype on the free tier first to hear the latency for yourself.

• Cartesia vs ElevenLabs: which should I use?

  ElevenLabs has the widest voice-cloning library and is the default for rich narration. Cartesia is built for speed: its Sonic 3 model returns the first byte of audio in about 90 milliseconds, roughly four times faster than the field. When latency is the deciding factor in a real-time voice build, Cartesia wins; when you need the largest voice catalog, compare ElevenLabs.

• What is Cartesia best for?

  Real-time voice work where latency makes or breaks the experience: phone and voice agents, live dubbing, and narration that has to keep pace with audio or video. The Line product lets you build a full voice-agent stack (TTS, STT, orchestration) on one platform across 40-plus languages.

• What are Sonic, Ink, and Line?

  They are Cartesia's three products. Sonic is text-to-speech (Sonic 3 is the ultra-low-latency model), Ink is speech-to-text, and Line is a platform for building voice agents end to end. Together they cover both directions of audio plus the orchestration to wire a full agent.

• How fast is Cartesia's Sonic model?

  Sonic 3 ships the first byte of audio in roughly 90 milliseconds, around four times faster than the field. In a voice agent, that is the difference between something that feels live and something that feels like a hold queue, which is why latency-sensitive builds reach for it.

More

• Cartesia docs

Alternatives to Cartesia

Other tools we'd consider for the same job.

• ElevenLabs

  Best-in-class voice synthesis and cloning. Used for podcasts, audiobooks, dubbing, and game narration

• Descript

  Edit video and podcasts by editing the transcript. Overdub voice cloning, studio sound, and agent clip creation

Other Audio tools

• ElevenLabs

  Best-in-class voice synthesis and cloning. Used for podcasts, audiobooks, dubbing, and game narration

• Suno

  Generate full songs from a prompt — lyrics, vocals, instrumentation. Stems available on paid plans

• Udio

  Song generation with extraordinary vocal quality. Strong at genre-specific styles and mashup prompts

• Otter.ai

  Live meeting transcription and summarisation. Integrates with Zoom, Google Meet, Teams — search across every call