Build conversational AI voice agents that sound human
Deploy conversational agents that handle interruptions, speak with natural inflections, and respond in under 800ms. Perfect for support, sales, and scheduling.
Engineered for production voice agents
Deploy production-ready voice agents with sub-800ms latency, automatic interruption handling, and native SIP telephony integration.
Ultra-Low Latency
Our custom WebRTC pipeline streams audio chunks in real-time, achieving sub-800ms response times that feel completely natural.
Smart Interruption
Agents stop speaking the millisecond they detect user speech, allowing for fluid, conversational turn-taking.
Custom LLM Support
Plug in your own custom LLM via WebSockets or use our optimized, pre-configured conversational models.
Global Telephony
Instantly provision phone numbers in 40+ countries, connect existing Twilio numbers, or integrate custom SIP trunks.
Experience the low-latency difference
Standard voice setups suffer from high latency and rigid turn-taking. Retell AI responds instantly and handles natural human interruptions.
Standard Voice Setup
~2,400ms LatencyRigid turn-taking. If you interrupt, the agent keeps talking, creating a chaotic and frustrating user experience.
Retell AI Engine
< 800ms LatencyFluid, human-like conversation. Try interrupting the agent mid-sentence to see how it stops speaking instantly.
Customize your agent's personality
Adjust the system prompt, select a voice profile, and fine-tune speaking parameters to match your brand's exact tone.
Live Agent Preview
CustomizedClick the button below to test your customized agent. Speak or type to interact.
Deploy with a single API call
Integrate Retell AI into your existing telephony stack or web application in minutes.
curl -X POST https://api.retellai.com/create-phone-call \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"agent_id": "agent_sarah_123",
"from_number": "+1234567890",
"to_number": "+1987654321",
"retell_llm_dynamic_variables": {
"customer_name": "John Doe"
}
}'Telephony Integration
Connect seamlessly with Twilio, Vonage, or bring your own SIP trunk.
Custom LLM Support
Use our optimized LLM engine or plug in your own custom LLM via WebSockets.
Real-Time Webhooks
Receive instant post-call transcripts, analysis, and structured data extraction.
Works with your existing stack
Retell AI integrates natively with leading telephony providers, LLMs, and developer tools.
Frequently Asked Questions
Technical details on WebRTC streaming, custom LLM integration, and telephony routing.
We use a custom-built, highly optimized WebRTC and WebSocket pipeline that streams audio chunks in real-time. By co-locating our speech-to-text, LLM, and text-to-speech engines in the same edge data centers, we eliminate round-trip network delays.
Yes! You can connect your own custom LLM via our WebSocket API. This allows you to use fine-tuned models, maintain custom state, and integrate with your internal databases in real-time during the call.
Our engine continuously listens even while the agent is speaking. The moment the user starts speaking, our speech-to-text engine detects voice activity, immediately stops the text-to-speech playback, and updates the LLM context with the new user input.
We support native integrations with Twilio and Vonage. You can also connect any custom SIP trunk or telephony provider that supports SIP/RTP streaming.