Vapi / Retell AI

Vapi AI is an API-first platform centered on customizability through code-based development. It gives technical teams maximum control over every component of AI phone agents with minimal templates or frameworks. Retell AI, an alternative platform, offers a managed voice AI infrastructure with an SDK and drag-and-drop builder enabling non-technical teams to launch production agents in three minutes. Retell supports unlimited concurrent calls on every plan, while Vapi's concurrency is more restrictive. Both platforms focus on different use cases: Vapi for engineers needing raw composability, Retell for developers wanting managed infrastructure. Voiceflow, Retell, and Vapi are the three dominant AI voice agent platforms in 2026.