Ultravox.ai
Verified Oct 15, 2026 ActiveSpeech-to-speech model and API for voice agents that skips the transcription step.
Listed on EffectHub ·
Pricing
- Pricing model
- Freemium
- Paid options from
- $0.05/min
- Billing
- Metered · per minute
Pay as you go has no monthly fee: the first 30 minutes are free, then $0.05 per minute, with a hard cap of 5 concurrent calls. Pro is $100 a month and removes the concurrency cap, adding 5 custom voices and 20 RAG corpora. SIP is $0.005 per minute ($0.0048 on Pro); threads are $2 per million input and $15 per million output tokens.
Use tool ↗About Ultravox.ai
Ultravox is voice-agent infrastructure built by the team formerly known as Fixie.ai and acquired by Inworld at the end of September 2026. Its model consumes audio directly instead of running speech through a transcriber first, which removes a hop from the response path and keeps tone and interruption handling that a text pipeline flattens. Developers get a REST API, web and mobile SDKs, SIP for phone calls, RAG corpora for grounding answers and custom voices, and the open-weight models are on Hugging Face. Billing is per minute of conversation, with separate token rates for the threads feature.
- Platforms
- Web · API
- API
- Yes
- Last verified
- Oct 15, 2026
Verified sources
- Pricing page: first 30 minutes free, then $0.05 per minute on Pay as You Go ($0/month, up to 5 concurrent calls); Pro $100/month; SIP 0.5 cents per minute; threads $2/$15 per million tokens (15 October 2026)ultravox.ai ↗
- Site banner states Ultravox has been acquired by Inworld (15 October 2026)ultravox.ai ↗
- Inworld announcement dated 30 September 2026: Inworld acquired Ultravox, existing accounts and agents keep working with no migration, built-in Inworld voices now run on Realtime TTS-2 (read 15 October 2026)inworld.ai ↗
- Home page describes speech-native agents with developer APIs and links the open-weight models on Hugging Face (15 October 2026)ultravox.ai ↗
Is Ultravox.ai legit?
We don’t label tools safe or unsafe. Below are the records we checked ourselves, each with the date we read it.
- Domain registered
- Oct 5, 2023 (3 years ago)Registry record (RDAP), registrar NameCheap, Inc., looked up Sep 12, 2026
- TLS certificate
- Issued by Let's Encrypt, valid until Jan 8, 2027Seen in our own connection to the site on Oct 15, 2026
- Last checked
- Oct 15, 2026The site answered
- Operated by
- Inworld AI, United StatesOur research, card verified Oct 15, 2026
Pros & cons of 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
Best for
- Developers building latency-sensitive voice agents
- Teams that want the option to self-host the model later
- Products needing SIP telephony alongside browser and mobile calls
Not for
- Non-developers looking for a drag-and-drop agent builder
- Anyone who needs an out-of-the-box CRM or helpdesk integration
Watch out: Inworld acquired Ultravox on 30 September 2026. Nothing has to migrate today, but pin a contract or watch the pricing page before committing a large deployment, since plans and APIs may be folded into Inworld's platform.
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