Cartesia vs Retell AI
A side-by-side comparison of Cartesia and Retell AI, two Voice tools, drawn from Ignaite's continuously-verified listings.
Compared from listings verified as of
At a glance
The honest brief
Cartesia
State-space Sonic models hit sub-100ms first audio — the latency floor for real-time voice agent loops.
- Streaming over WebSocket for fast first audio
- State-space architecture, not transformer
- Streaming-first WebSocket protocol depth
- Cost-competitive at scale
- Long-form expressive texture trails ElevenLabs
- Fewer voices than ElevenLabs catalog
- API-only, no end-user app
Retell AI
Bring your own LLM behind the voice agent, so it isn't locked to a single model like most all-in-one voice platforms.
- Inbound and outbound call handling
- SIP/Twilio telephony built in
- Low-latency turn-taking model
- No-code builder plus API
- Per-minute costs stack with LLM/TTS
- Voice quality depends on chosen vendors
- Cloud-only, no self-host