Vapi
Build and deploy voice AI agents that handle phone calls, SMS, and chat at enterprise scale with sub-500ms latency.
Alternatives
Overview
Vapi is a developer platform for building, testing, and deploying voice AI applications, phone-based agents that handle inbound and outbound calls with the sub-500ms response latency required for natural conversation. The core challenge in voice AI is latency: stitching together speech-to-text, LLM inference, and text-to-speech independently produces delays that make conversations feel broken and unnatural. Vapi handles the entire stack, STT, LLM routing, TTS, interruption handling, turn management, and call lifecycle management, with optimized latency that makes conversations feel responsive. Teams use it to build appointment booking bots, customer service agents, sales dialers, outbound reminder systems, and intake flows that operate at scale without human agents.
The dashboard provides a no-code interface for configuring agent behavior: conversation flow, fallback handling, escalation triggers, and CRM integration for call logging. Testing tools simulate calls with specified scenarios before production deployment. Vapi supports a wide range of underlying models (GPT-4o, Claude, Gemini, custom fine-tuned models) and voices (ElevenLabs, Cartesia, Deepgram). Call analytics include transcripts, sentiment analysis, keyword tracking, and outcome logging.
Free to start; usage-based pricing charges per minute of call time. Vapi is the dominant developer-facing voice AI infrastructure platform, most voice agent builders in the space use Vapi for its reliability, API design, and the completeness of its voice-specific tooling.
Key Features
- Sub-500ms latency
- Inbound and outbound calling
- Bring your own LLM
- Voice interruption handling
- Call analytics and transcripts
- Webhooks for custom logic
- • Best latency in the voice AI category
- • Flexible model and voice provider support
- • Strong developer documentation
- • Usage costs can scale quickly at volume
- • Requires developer setup, not no-code
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