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
| Attribute | Cartesia | Retell AI |
|---|---|---|
| Category | Voice | Voice |
| Pricing | FREEMIUM | FREEMIUM |
| License | Proprietary | Proprietary |
| Deployment | Cloud | Cloud |
| Platforms (differs) | API | Web, API |
| Model support (differs) | Single model (proprietary) | Multi-model |
| Vendor (differs) | Cartesia | Retell AI |
| Capabilities (differs) |
|
|
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
When to pick which
Both cover Voice agent.
Pick Cartesia if you need Speech synthesis (TTS), Transcription (STT), and Voice cloning.
- Speech synthesis (TTS) (primary capability)
- Transcription (STT) (secondary capability)
- Voice cloning (secondary capability)
Pick Retell AI if you need Tool / function calling and AI app builder.
- Tool / function calling (secondary capability)
- AI app builder (primary capability)
Retell AI leans on Voice agent as a headline capability; Cartesia treats it as secondary.
- Voice agent (primary capability)
They also differ on:
- Platforms
- API · Web, API
- Model support
- Single model (proprietary) · Multi-model