Vapi
Full-stack platform for building, testing, and deploying voice AI agents. Handles real-time telephony, multi-provider LLM routing, interruption detection, and call analytics. Most-adopted voice agent infrastructure in production.
ElevenLabs
State-of-the-art TTS API with voice cloning, multilingual support, and low-latency streaming. Used in podcasts, audiobooks, conversational AI agents, and game NPCs.