Cartesia
Power voice agents with sub-100ms TTS that streams in real time. Sonic's architecture eliminates the latency pause that makes voice bots feel robotic.
Cartesia — the verdict: Developers building conversational voice agents where natural back-and-forth pacing matters most Cartesia is built specifically for developers shipping conversational voice agents where latency is the actual problem. Pricing: Free 10K characters/mo / $65/mo Growth. Last reviewed: August 2026.
Best For
Developers building conversational voice agents where natural back-and-forth pacing matters most
Standout Feature
Sub-100ms text-to-speech latency via a streaming architecture that eliminates the turn-taking pause other TTS models have
Verdict
The fastest conversational voice latency available, ElevenLabs still wins on richness and nuance of the voice itself.
Alternatives
Overview
Cartesia is a real-time voice AI platform built on Sonic — a state-space model architecture that delivers sub-100ms text-to-speech latency, making natural conversational AI and live voice agents practical. Unlike autoregressive TTS models that generate audio sequentially, Sonic streams output as it processes input, eliminating the turn-taking pause that makes voice bots feel robotic. Used in production by voice AI products that need human-paced conversation.
Our Take
Cartesia is built specifically for developers shipping conversational voice agents where latency is the actual problem. The sub-100ms text-to-speech response from its Sonic architecture eliminates the perceptible pause that makes most voice bots feel mechanical during back-and-forth conversation. If you're building a customer-facing voice agent or a real-time assistant where turn-taking naturalness matters, this is where to start. For narration, audiobooks, or any non-conversational use case, ElevenLabs has richer voice quality and is the better pick.
Key Features
- Sub-100ms time-to-first-audio for real-time voice applications
- Streaming TTS — output starts before the full text is processed
- 50+ voices across accents and languages
- Voice cloning from a short audio sample
- Emotion and pacing control via SSML-style tags
- WebSocket API for low-latency real-time integration
- • Fastest TTS latency available — essential for conversational voice agents
- • Streaming architecture enables natural back-and-forth conversation pacing
- • Voice quality is competitive with ElevenLabs at significantly lower latency
- • Premium voice quality still trails ElevenLabs on richness and nuance
- • Voice cloning requires more audio samples than some competitors
- • Growth plan pricing scales steeply with volume
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