Retell AI
by Retell AI
Developer platform for building, deploying and monitoring AI phone agents, billed per minute
Retell AI is a voice AI agent platform for engineering and contact-center teams that want to automate inbound and outbound phone calls. You assemble the agent from your choice of LLM, voice and telephony, and Retell runs the real-time call, handles interruptions and transfers, and logs every call for QA.
Retell AI, founded in 2023 and backed by Y Combinator, sells the runtime for AI phone agents. A customer picks an LLM, a text-to-speech voice and a telephony route (Twilio, Vonage or its own SIP trunk), and Retell manages the live call: turn-taking, mid-sentence interruptions, IVR navigation, DTMF, warm transfer to a human and voicemail detection. Agents are built in a drag-and-drop conversation-flow editor or through the API and SDKs, and every call is transcribed and available for post-call analytics. The vendor quotes roughly 600ms response latency and cites a Cekura benchmark of 95.7% workflow accuracy on multi-step calls; both figures are vendor-reported. Pricing is pay-as-you-go: $0.055 per minute for Retell's voice infrastructure, plus pass-through LLM, TTS and telephony charges, which the pricing page puts at $0.07 to $0.31 per minute all-in. The 2026 changelog shows a fast cadence: an AI QA analyst (January), agent guardrails and auto-failover (February), A/B testing (March), Agent Versioning 2.0 (May), live call monitoring and a built-in CRM (June), the Conductor build-and-simulate copilot (July) and Retell Workflows orchestration (August 2026). Sacra estimates annualized revenue reached $80M by August 2026, on about $5.1M of disclosed funding. It sits in the developer-first voice tier alongside Vapi and Bland AI, below turnkey contact-center suites.
A contact-center or CX engineering team with developers on hand, automating high-volume, scripted phone calls such as scheduling, intake or collections.
Production phone agents with interruption handling, warm transfer and full call QA, without building the real-time voice stack yourself.
At a Glance
- Category
- Audio & Voice
- Pricing
- Usage-based, Contact for pricing
- Target Market
- CTOs, Contact Center Leaders, Enterprise Developers, Healthcare Operations
- Deployment
- Cloud-only, API-based
- Founded
- 2023
- Headquarters
- Palo Alto, United States
- Customers
- Thousands of businesses (vendor/Sacra); 40M+ calls per month reported in 2026
Key Features
- ✓Conversation flow builder
Drag-and-drop node editor with reusable components and node-level knowledge bases, so scripted calls stay on a predictable path.
- ✓Real-time turn-taking
Handles callers who interrupt mid-sentence and adapts voice speed to the caller, which keeps calls from sounding robotic.
- ✓Warm transfer to humans
AI-assisted handoff passes the call and its context to a live agent, with caller ID control on the transfer.
- ✓AI QA and live monitoring
Every call is transcribed and auto-reviewed, with live call monitoring, custom alerts and dashboards for ops teams.
- ✓Agent versioning and A/B testing
Multi-draft versions with environment tags and traffic splitting let teams test prompt changes on live calls before full rollout.
- ✓Guardrails and PII removal
Optional add-ons block jailbreak attempts and harmful output and redact personal data from transcripts, priced per minute.
- ✓Bring-your-own telephony
Connects to Twilio, Vonage or existing phone systems over SIP, with branded caller ID and verified numbers.
Capabilities
Use Cases
- •Healthcare scheduling
Clinics such as Pine Park Health use voice agents to book and confirm appointments, freeing front-desk staff for in-person patients.
- •Collections outreach
Medical Data Systems runs outbound collections calls, with the agent verifying identity and routing disputes to human collectors.
- •Product support triage
SWTCH uses an agent for EV charging support, resolving routine issues on the first call and escalating the rest with context.
- •After-hours inbound coverage
An agent answers overflow and night calls, captures the request into a CRM and books a callback, so no lead goes to voicemail.
Ideal For
Best For
- ✓Appointment scheduling and patient intake calls in healthcare, with a HIPAA BAA on Enterprise
- ✓Outbound collections and payment reminder campaigns at high concurrency
- ✓Inbound support triage that hands off to a human agent mid-call with context
- ✓Teams that want to swap LLM, voice and telephony providers without rebuilding the agent
Not Ideal For
- ✗Non-technical business teams: G2 reviewers and independent reviews cite a steep learning curve, and real deployments need engineering time
- ✗Buyers who need a fixed monthly cost: per-minute billing stacks LLM, TTS, telephony and add-ons, so spend varies with call length and model choice
- ✗Revenue teams wanting omnichannel outreach out of the box: the platform covers voice, SMS and web chat, with no email or LinkedIn sequencing
Integrations
Deployment
Market & Ratings
Thousands of businesses (vendor/Sacra); 40M+ calls per month reported in 2026
Market Analysis
Pros
- ✓Very high reviewer satisfaction: 4.8/5 across 2,638 G2 reviews
- ✓Transparent per-minute list pricing with a free starting credit and 20 free concurrent calls
- ✓SOC 2 Type II, HIPAA, GDPR and ISO 27001 claimed, with a BAA available for healthcare
- ✓Rapid 2026 shipping cadence on QA, guardrails, versioning and orchestration
Cons
- ✗Total cost is hard to forecast: independent reviews show a 5,000-minute month ranging from $650 to $1,550 depending on model and add-ons
- ✗Steep learning curve for non-technical users; independent reviews estimate meaningful engineering effort to deploy
- ✗G2 reviewers flag pricing pressure for small operations and occasional technical issues on specialised flows
- ✗Developers on Hacker News report building their own pipelines on open components to cut cost well below Retell's rates
Pricing
Pay-as-you-go
$0.07-$0.31/min (voice); chat from $0.002/message
- ✓$10 free credits to start
- ✓20 free concurrent calls, then $8/month per extra slot
- ✓Community and email support
- ✓Per-second billing, no per-call rounding
Enterprise
Contact for pricing
- ✓No concurrency cap
- ✓HIPAA BAA, SSO and custom terms
- ✓Role-based access control
- ✓24/7 dedicated support and implementation help
Billing is per second of call time: $0.055/min for Retell's voice infrastructure plus LLM ($0.04-$0.64/min depending on model), TTS ($0.015-$0.10/min) and telephony (about $0.015/min in the US). Knowledge base, denoising and guardrails add $0.005/min each, PII removal $0.01/min. Silence is billed while speech-to-text runs, failed calls are free. HIPAA BAA, SSO and uncapped concurrency are Enterprise-only.
Security & Compliance
Sources
This page was written from 7 sources, 4 on domains other than retellai.com.
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