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Vapi is the leading voice AI infrastructure platform for developers building conversational phone agents. Used by teams at startups and Fortune 500 companies alike, Vapi provides the APIs, SDKs, and real-time audio pipeline needed to create voice agents that handle inbound support calls, run outbound campaigns, qualify leads, schedule appointments, and automate any phone-based workflow -- all with sub-500ms response times that make interactions feel genuinely human.

With over 300 million calls processed, 2.5 million assistants launched, and 500,000 developers on the platform, Vapi has become the default infrastructure layer for teams that want to build voice AI the right way: with full control over their stack and no artificial ceilings on what they can create.

Key Features

• Sub-500ms Latency: Vapi's custom real-time audio infrastructure delivers near-instant responses, enabling natural turn-taking and fluid conversations that don't feel like talking to a bot.
• Bring Your Own Models: Choose your own LLM (GPT-4, Claude, Gemini, Groq, Mistral), your own speech-to-text provider (Deepgram, AssemblyAI, Azure), and your own text-to-speech voice (ElevenLabs, PlayHT, Cartesia) -- or plug in your own self-hosted models.
• Inbound & Outbound Calling: Deploy agents to handle incoming customer calls or run outbound campaigns at scale. Supports web, iOS, Android, and direct telephony integration.
• Tool Calling & API Integration: Connect your existing APIs as tools that agents can call mid-conversation -- fetching customer data, booking appointments, checking order status, or triggering actions in your backend in real time.
• Flow Studio: A visual drag-and-drop builder for designing conversational flows inside the dashboard, alongside full API and SDK access for programmatic control.
• Automated Testing: Build test suites using simulated voice agents to catch hallucination risks and edge cases before pushing to production.
• A/B Experiments: Test different prompt variations, voices, and conversation flows simultaneously to continuously optimize agent performance.
• Multilingual Support: Deploy agents in 100+ languages via integrated providers, including Microsoft Azure, with no need to build separate systems per market.
• Interruption Handling & Backchanneling: Vapi detects when callers speak over the agent and responds naturally, with built-in backchanneling to keep conversations feeling smooth during processing delays.
• 40+ Integrations: Native connections to Twilio, Salesforce, HubSpot, Zendesk, Google Calendar, Zapier, Make, Slack, Clay, GoHighLevel, and more.

What Makes Vapi Unique

Vapi is built as middleware -- the infrastructure layer that sits between your telephony provider, your AI models, and your application logic. This means you're never locked into a single vendor's voice or LLM quality. If a better model launches tomorrow, you can swap it in. If you need to run on your own self-hosted infrastructure, Vapi supports that too. The platform gives developers thousands of configuration points while still being fast enough to go from prototype to production in days, not months.

Why Use Vapi

Whether you're automating a customer support line, running outbound lead qualification at scale, building an AI receptionist, or embedding voice agents into your product, Vapi gives you the infrastructure to do it without building the real-time audio pipeline from scratch. It's the platform teams choose when they need maximum control, maximum performance, and the freedom to own every part of their voice AI stack.