Ultravox.ai vs Vapi

Ultravox.ai

Still one of the few voice stacks where the model itself is the product rather than glue over someone else's transcriber, and the open weights on Hugging Face keep a self-hosting exit open. Inworld bought it at the end of September 2026; accounts and agents keep running unchanged for now, but new builds should expect the roadmap to move toward Inworld's own speech-to-speech offering. It remains a builder's tool, so budget engineering time as well as per-minute cost.

Pros

• +Model takes audio directly, removing the transcription hop from the response path
• +Open-weight models published on Hugging Face allow self-hosting
• +REST API plus web and mobile SDKs, and SIP for phone calls
• +RAG corpora and custom voices are part of the platform, not add-on services
• +Pay as you go has no monthly floor, so a prototype costs only what it talks

Cons

• −Free tier is capped at 5 concurrent calls, so load testing needs a paid plan
• −Custom voices and RAG corpora are capped even on the $100 Pro tier
• −Threads bill separately per token on top of per-minute conversation cost
• −Product direction now depends on its new owner, Inworld

Vapi

The default answer when a developer needs a voice agent on a phone line rather than a chat widget: it handles the hard real-time parts — barge-in, latency, turn-taking, telephony — and lets you swap in your own models. Enterprise adoption at Ring and Intuit is real validation. Cost forecasting is the hard part, because the platform fee is only one of four meters running.

Pros

• +Handles real-time voice mechanics: turn-taking, interruptions, latency and telephony
• +Bring-your-own-key support across OpenAI, Anthropic and Google avoids double model markup
• +CRM and helpdesk integrations for Salesforce, HubSpot and Zendesk
• +SOC 2, HIPAA and PCI compliance plus SSO and RBAC on the enterprise tier
• +Proven at scale, with Amazon Ring routing inbound support volume through it

Cons

• −The $0.05/minute platform fee sits on top of speech, model and voice provider costs
• −Concurrency beyond ten lines costs $10 per line per month
• −Enterprise compliance features require an annual Scale contract
• −It is a developer platform, so there is no usable no-code path

Is Ultravox.ai cheaper than Vapi?

Both publish the same entry price, $0.05/min. The difference is what each plan includes, which the fact table above sets side by side.

Does Ultravox.ai or Vapi have a free tier?

Ultravox.ai has a free tier; Vapi has paid plans only.

Which has a public API, Ultravox.ai or Vapi?

Both ship a public API, so either can be built on; the fact table above shows the platforms each one runs on.