Retell AI vs Synthflow vs Vapi

Founded in 2023, Retell AI is built by a tight-knit team of founders with rich backgrounds at Google, Meta, TikTok, ByteDance, and more. We launched publicly in early 2022, were accepted into Y Combinator in November 2023, and raised $4.6M in seed funding in May 2024 to propel innovation further.

Retell AI's mission is to transform how businesses connect with customers—creating AI voice agents that break communication barriers and create smoother, more responsive experiences.

Synthflow AI is a no-code platform that empowers businesses to create and deploy sophisticated AI-powered voice assistants to automate phone calls. These assistants can handle both inbound and outbound calls, engaging in human-like conversations to perform a variety of tasks, thereby enhancing customer service and operational efficiency.

Synthflow AI offers extensive integration capabilities with popular CRM systems such as HubSpot and Freshworks, as well as other applications through tools like Zapier and Make.com. This allows for seamless data flow and workflow automation.

Vapi.ai offers a cutting‑edge voice-driven UI/UX and SDK for devs. Integration with platforms like iOS shortcuts or React via NPM has been attempted by some developers. Build, test, and deploy advanced voice AI agents in minutes with Vapi. The platform for developers creating conversational voice AI. 

It combines speech-to-text, large language models (LLMs), and text‑to‑speech, giving you full control over each component—such as choosing providers like OpenAI, Anthropic, Deepgram, ElevenLabs, and others. Vapi CEO Jordan Dearsley shares how Vapi grew to $8M over the past 5 years. Vapi has raised $20.1M and hit a $13.5M valuation in 2025.