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Retell

Freemium
voice aiconversational aiapideveloper toolstext-to-speechspeech recognitionsaastelephonylow latencyllm

Retell is a developer-first API for building ultra-low-latency, human-like conversational voice agents, enabling businesses to create sophisticated voice bots that can handle complex interactions with natural-sounding speech.


Retell AI provides a specialized API for developers to construct highly responsive, conversational voice agents. The platform's core focus is on minimizing latency to sub-100ms, creating a more natural and human-like interaction flow that traditional voice bots often lack. It serves businesses and developers who need to integrate sophisticated voice automation into their products, such as for customer service, sales outreach, or in-app assistants. Retell's unique value proposition lies in its model-agnostic architecture, which allows developers to plug in their preferred large language models (LLM), speech-to-text (STT), and text-to-speech (TTS) engines. By managing the complex telephony and real-time streaming infrastructure, Retell enables developers to focus on crafting the conversational logic rather than the underlying plumbing.

Pros

  • Extremely low latency (sub-100ms claimed) for more natural, real-time conversations.
  • Model-agnostic design allows developers to use any LLM, STT, and TTS provider.
  • Advanced conversational features like interruption handling, backchanneling, and realistic turn-taking.
  • Manages complex telephony infrastructure (PSTN, WebRTC), simplifying deployment.
  • Provides both inbound and outbound calling capabilities.
  • Includes a web calling SDK for easy integration into front-end applications.

Cons

  • Primarily an API-first platform, which requires significant coding expertise and lacks a no-code interface.
  • Usage-based pricing can be complex to forecast and may become costly for high-volume use cases.
  • As a newer company, its community support and documentation may be less extensive than more established competitors.
  • Overall performance and reliability are dependent on the third-party LLM, STT, and TTS services it is connected to.

Key features

  • Low-latency conversational voice API
  • Bi-directional audio streaming
  • Support for custom LLMs, STT, and TTS integrations
  • Built-in telephony for PSTN calls
  • Web calling SDK for browser-based voice chats
  • Dynamic interruption and turn-taking logic
  • Agent memory and retention for coherent conversations
  • Outbound and inbound call management

Integrations

OpenAI (GPT-4, etc.)Anthropic (Claude)Google (Gemini, Speech-to-Text)Deepgram (STT, Aura TTS)ElevenLabsTwilio (as a telephony provider)VonageBandwidth

Target audience

Developers, product managers, and businesses seeking to build and integrate advanced, low-latency voice AI capabilities into their applications for customer support, sales, or user engagement.


Ratings & Reviews

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Key Metrics

Founded

2023

Headquarters

San Francisco, USA

Pricing Tiers

Free

60 free minutes per month, 1 concurrent call, access to beta features, and community support. Ideal for hobbyists and initial development.

Free

Starter

120 free minutes per month, up to 10 concurrent calls, and standard support. Usage fees apply per minute for agent model and telephony.

$10/mo + usage

Enterprise

Custom concurrent calls, custom minutes, dedicated support, custom data retention policies, and optional on-premise deployment.

Custom


Frequently Asked Questions


Top Alternatives to Retell

Vapi

Vapi is a direct competitor also offering a developer-first API for building low-latency voice AI agents, often chosen for its similar feature set and developer experience.

Twilio Voice API

Twilio is an established CPaaS giant that provides broader telephony tools, which someone might choose for its vast ecosystem, though it requires more assembly to achieve what Retell offers out-of-the-box.

Bland AI

Bland AI is a close alternative focused on simplifying the process of creating and deploying voice agents for automating phone calls, appealing to those who prioritize speed of deployment.

Deepgram

Primarily an STT/TTS provider, Deepgram's Aura platform lets you build voice agents, which is a good choice if you prefer a solution from a single, vertically integrated speech AI vendor.

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