Cartesia

Audio

Cartesia is a real-time voice AI company whose Sonic model delivers ultra-low-latency text-to-speech for voice agents. It is purpose-built for real-time, sub-second synthesis as infrastructure, prioritizing speed for live voice agents over content tooling.

How to use Cartesia

Create an account and call the Sonic model through the API, or test it in the playground, with your text and a chosen voice. It is billed per character, so estimate cost from your output volume. It suits being embedded in a voice-agent stack rather than one-off content.

Best for

Low-latency, real-time speech for conversational voice agents. Streaming synthesis where response time is critical. Developer and API-first voice infrastructure.

How it behaves

Character-based billing where one credit equals one character of output. The flagship Sonic model is tuned for ultra-low latency, and the free tier is personal and non-commercial.

Tips

Estimate cost from output character count. Use it inside a live agent stack, not for one-off narration. Prototype in the playground before wiring the API.

Pricing

Free tier with a monthly allowance for non-commercial use. Paid tiers scale up to a few hundred dollars a month, working out to roughly $5 to $37 per million characters.