Ultravox

Build fast, human-like voice AI agents with speech-native intelligence, low latency, and developer-friendly REST APIs and platform SDKs.

Freemium speech processing

Free plan available

$100/mo

About Ultravox

Ultravox is an audio intelligence infrastructure platform and research lab designed to power real-time, conversational voice AI agents. Most legacy voice AI stacks convert speech to text before feeding it into an LLM, causing high latency and stripping away expressive paralinguistic cues like pitch, cadence, and tone. Ultravox solves this by utilizing a speech-native architecture and running models on dedicated, purpose-built inference infrastructure to deliver fluid, natural conversations without shared inference pool delays. The platform combines open-weight speech models—such as Ultravox v0.7—with dynamic endpointing powered by UltraVAD v0.1. This proprietary neural voice activity detection accurately distinguishes between normal speech breaks, thoughtful pauses, and the actual end of a speaker's turn. Developers can integrate voice capabilities into web, mobile, and telecommunication systems using developer-friendly REST APIs, platform SDKs, and built-in integrations for major telephony and SIP providers. Ultravox is primarily designed for developers, engineering teams, and enterprise growth or support operations seeking to deploy responsive conversational agents. It supports features like outbound call scheduling, retrieval-augmented generation (RAG) across multiple corpora, and custom voice cloning, making it suitable for automated customer care, sales development, and mobile voice assistants. What sets Ultravox apart from conventional pipeline setups is its unified, speech-native approach. Instead of daisy-chaining separate ASR, LLM, and TTS vendors, Ultravox directly manages its end-to-end inference stack and foundational models. This delivers top-tier reasoning performance—scoring up to 97% on Big Bench Audio with thinking enabled—while drastically cutting down round-trip response times.

Ultravox pros & cons

Pros

Processes speech natively without intermediary text transcription, preserving vocal inflection and lowering latency.
Scores up to 97% on Big Bench Audio benchmarks with thinking enabled.
Provides 30 minutes of free call time and unlimited playground testing to start building.
Open-weight models are made accessible to the developer community on Hugging Face.

Cons

The free Pay as You Go tier enforces a hard cap of 5 concurrent calls.
Features like the Outbound Call Scheduler and expanded RAG corpora require an upgrade to the $100/month Pro plan.

Ultravox use cases

Software engineers can integrate real-time, responsive voice bots into web and mobile applications using REST APIs and SDKs.
Sales and growth teams can deploy automated outbound voice agents with scheduling and custom voice cloning to conduct phone outreach.
Customer support operations can connect SIP telephony directly to Ultravox models to handle inbound caller inquiries without robotic delays.

Ultravox features

outbound call scheduling
unlimited web playground access for testing
corpora management for voice rag
custom voice cloning capabilities
telephony and sip provider integrations
developer-friendly rest apis and cross-platform mobile/web sdks
ultravad neural voice activity detection and dynamic endpointing
speech-native foundational model (ultravox v0.7)

Ultravox pricing

Is Ultravox free? Yes, Ultravox has a free plan, and paid plans start at $100 / month.

Pay as You Go

Free

30 minutes of free calls
$0.05 per minute after free minutes
Up to 5 concurrent calls
Unlimited playground calls
No surge pricing
1 custom voice clone
2 corpora for RAG
SIP pricing at $0.005 per minute
Threads pricing: $2.00/1M input tokens, $15.00/1M output tokens (cached inputs free)

Pro

$100 / month

Everything in Pay As You Go
Billed yearly
No hard caps on concurrency
Outbound Call Scheduler
5 custom voice clones
20 corpora for RAG
SIP pricing at $0.0048 per minute
Never surge pricing

Enterprise

Price varies

Custom pricing per minute and SIP
No hard concurrency caps with priority concurrent calls
Priority SLA and response SLA
Organizational support
Customizable voice clones and RAG corpora
Custom outbound scheduling

Ultravox FAQs

What is Ultravox's approach to voice AI?

Ultravox uses a speech-native model rather than converting speech to text first. This prevents the loss of vital paralinguistic signals such as tone and cadence while significantly minimizing latency.

How much does Ultravox cost after the free trial?

Ultravox includes 30 free minutes. After the initial free minutes, call execution costs $0.05 per minute on both the Pay as You Go and Pro plans.

How does Ultravox handle turn-taking during conversations?

Ultravox uses UltraVAD, a neural voice activity detection model that predicts conversation states. It differentiates between thoughtful pauses and the end of a speaking turn to ensure smooth interruptions and replies.

Can I integrate Ultravox with existing phone networks?

Yes, Ultravox includes built-in telephony support and SIP integrations. SIP usage is billed at 0.5¢ per minute on Pay as You Go and 0.48¢ per minute on the Pro tier.

Are the Ultravox AI models open to the public?

Yes, Ultravox is built on open-weight models. The team shares its core research and model weights publicly on Hugging Face.

Ratings & reviews

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