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Retell AI

Retell AI

Infra for Building Conversational Voice AI

We help developers implement human-like voice agents in a day instead of months. Plug in your LLM, a voice agent is born! From AI-powered call agents to voice-enabled coaching apps and lifelike companions, we are your trusted ally in turning these visions into reality. Although Voice AI has been around for some time, it hasn't yet become effective enough for mainstream use, primarily because of poor user experience. Conversational flows often feel awkward with unnatural pauses and interruptions, requests are frequently misunderstood, and voices sound robotic or overly dramatic. On top of that, setting up such a Voice AI system can require upwards of 100 hours of frustrating development. By offering a truly conversational, fast, and empathetic Voice AI that can be easily configured for any industry and integrated into any product, we aim to push the boundary of user-friendliness to a new level, reaching the threshold for mainstream adoption of Voice AI. We are at a pivotal moment in history where Voice AI will become the primary interface for accessing products and services, revolutionizing our interactions with machines for the better. Retell AI is at the forefront of creating this new reality.

Retell AI
Founded:2023
Team Size:5
Location:San Francisco
Group Partner:Michael Seibel

Active Founders

Bing Wu

Co-founder & CEO at Retell AI. Enthusiastic about the human brain and AI, Bing spent three years as a product manager at ByteDance/TikTok, where he led B2B and consumer products that delighted billions. Before joining ByteDance/TikTok, Bing founded two investor-backed startups in college, generating six-figure revenues.

Todd Li

Todd is the founder of several venture-backed startups. Before his startup journey at Retell, Todd worked at Google Ads as a software engineer.

Evie Wang

Evie is the Co-founder and CMO of Retell AI She has a design background and a deep understanding of B2B business as she spent 3 years as a Product Designer at Bytedance.

Evie Wang
Evie Wang
Retell AI

Weijia Yu

Weijia excels in product and software development, with a specialization in machine learning. At Meta, he spent three years as a PM hybrid Tech Lead within Facebook product team. Prior to Meta, Weijia led app development at ObEN, a Series B AI tech startup, providing full-stack AI solutions including TTS(text-to-speech), computer vision and chatbot.

Weijia Yu
Weijia Yu
Retell AI

Zexia Zhang

Zexia is the co-founder and CTO of Retell AI. Passionate about ML, Zexia is always at the frontier of advancing speech technologies. Before Retell, Zexia spent four years at Google where he led the development of next-gen speech translation experience, and NLP solutions for call analysis.

Zexia Zhang
Zexia Zhang
Retell AI

Company Launches

Tl;dr: You can now use our API to build human-like voice AI agents with your LLM. We've achieved response times averaging 800ms, reaching the level of human interactions. (see our demo or call +1 (415) 831-7577 to try it out).

Problem — Building human-like voice AI agents is hard

  • Human-like interaction is hard: Building a voice AI agent that can talk seems easy (stitching together speech-to-text, LLM, and text-to-speech), but making it interact like humans is hard. In human conversation, one has to respond fast and handle all kinds of situations (handling interruptions, knowing when it's your turn to speak, etc).

  • Long development time: Developers building voice products spend hundreds of hours focusing on the voice conversation experience alone.

  • Quality often falls short: Current voice AI products often have long response latency (>3s), do not know when to appropriately speak (might interrupt you too much, or respond not quickly enough), and do not handle user interruptions well (AI and human talking over each other), and the list goes on.

Solution — API for building human-like voice AI agents

  • Human-Like Conversations: With our API, you can build a superior voice conversation experience with your LLM. We've achieved response times averaging 800ms, reaching the level of human interactions. We also handle interruptions and provide smart turn-taking determination to achieve seamless conversational exchanges.

  • Connect your LLM easily: Plug in your LLM and create a human-like voice agent easily.

  • WebSocket Support: Connect directly with your users through your web frontend or via phone. You won't have to manage audio bytes – we'll handle that for you.

Who is this product meant for?

Anyone building a voice experience can benefit from using Retell AI. Whether you're developing AI call agents, AI coaching apps, or AI lifelike companions, we are your trusted ally in creating the best conversational experience for your users.

How to get started?

Have questions?

Our Ask:

  • Give us a try! We provide founder's support dedicated to helping you succeed. Please don't hesitate to schedule a meeting with us anytime!

  • If you know anyone who could benefit from Retell AI, we would appreciate a warm introduction. :)

Warm regards from the five-founders' team. (From left to right: Todd, Weijia, Zexia, Bing & Evie)

YC Sign Photo

YC Sign Photo