Ultravox
Ultravox (operated by Fixie.ai Inc.) provides the Ultravox Realtime platform, a speech-native voice AI infrastructure that enables developers and enterprises to build real-time conversational agents via direct audio inference without transcription.
- Company typePrivate
- Founded2023
- HeadquartersSeattle, United States
- Headcount11–50
- GTM typeB2B
- OfferingSoftware
What Ultravox does
Ultravox, operated by Fixie.ai Inc. and headquartered in Seattle, Washington, is a research lab and product company building speech-native voice AI infrastructure for developers and enterprise voice agent teams. Its core technology is the Ultravox Realtime platform, powered by the proprietary Ultravox v0.7 model built on a GLM 4.6 backbone (355B parameters, 160 experts per layer). Unlike cascaded voice stacks that transcribe speech to text before LLM inference, Ultravox performs reasoning directly on audio signals, preserving paralinguistic cues such as tone, cadence, and pitch while delivering approximately 900ms end-to-end latency. The platform also includes the UltraVAD v0.1 neural endpointing model for turn-taking detection and exposes a dedicated inference stack the company manages end-to-end.
The product is delivered through REST APIs, WebSockets, and SDKs spanning JavaScript/TypeScript, Python, React Native, Swift, Kotlin, and Flutter, with native telephony integrations for Twilio, Voximplant, Telnyx, Plivo, and jambonz, and voice output options including Inworld, ElevenLabs, Cartesia, LMNT, Google, and Respeecher. Pricing is anchored on a freemium + usage-based model at $0.05 per minute (30 free minutes monthly), a $100/month Pro subscription that lifts concurrency caps and adds voice cloning and RAG corpora, and custom Enterprise contracts for large-scale deployments with priority SLA.
Ultravox targets developers building voice agents for customer service, lead qualification, and appointment scheduling, as well as enterprise buyers in verticals such as healthcare and e-commerce. Distribution combines product-led growth (self-serve sign-up, free tier, Discord community, GitHub SDKs, Hugging Face open weights) with a sales-led enterprise motion via Request a Demo. The company has raised approximately $17 million across a 2022 seed and a February 2023 Series A led by Redpoint, grew its customer base 18x and its traffic 38x in 2025, and operates with a team of approximately 11 people.
Ultravox firmographics
Firmographics- Name
- Ultravox
- Legal name
- Fixie.ai Inc.
- Website
- https://ultravox.ai
- Company type
- Private
- Founded year
- 2023
- Operating status
- Operating
- Headcount range
- 11–50 employees
- Short description
- Ultravox (operated by Fixie.ai Inc.) provides the Ultravox Realtime platform, a speech-native voice AI infrastructure that enables developers and enterprises to build real-time conversational agents via direct audio inference without transcription.
- Ownership category
- akta.pro rank
Ultravox industry classification
Industry- Product category
- Voice AI Platform
- NAICS
- Computer Systems Design and Related Services (54151), Custom Computer Programming Services (541511), Translation and Interpretation Services (541930)
- SIC
- Services-Computer Programming Services (7371), Services-Computer Integrated Systems Design (7373), Services-Telephone Interconnect Systems (7385), Services-Computer Programming, Data Processing, Etc. (7370)
- akta.pro primary industry
- Voice Assistants & Voice UI (VUI) (HDAAAFAD)
Keywords
Where Ultravox is headquartered
LocationHeadquarters
- HQ city
- Seattle
- HQ country
- United States
- HQ region
- North America
Offices1 record
Markets served
Ultravox business model
Business model- GTM type
- B2B
- Offering type
- Software
- Cost components
- Technology or R&D, Infrastructure, Personnel, Operations, Marketing or Sales
Revenue model
- Usage-based Voice AI (Pay As You Go): Primary revenue stream based on per-minute usage of voice AI calls. Includes 30 free minutes per month, then $0.05 per minute for speech processing and TTS. No hard caps on total usage but limited to 5 concurrent calls on free tier.
- Pro Subscription: Monthly subscription at $100/month (billed annually) providing unlimited playground calls, no hard caps on concurrency, outbound call scheduler, 5 custom voice clones, and 20 corpora for RAG. Includes $0.05/min usage at the same rate as Pay As You Go.
- Enterprise Custom: Custom pricing for massive scale deployments with priority SLA, organizational support, and fully customizable platform features. Sold via sales-led motion through Request a Demo.
- SIP Telephony: Additional usage-based revenue from SIP call handling at 0.5¢/minute (Pay As You Go) or 0.48¢/minute (Pro). Bridge transfers incur additional costs as SIP infrastructure remains active.
- Threads (Token-based): Charges for token usage in thread-based conversations: $2.00 per 1M input tokens (uncached), $15.00 per 1M output tokens. Cached input tokens are free.
Pricing tiers
| Model | Billing | Price |
|---|---|---|
| Freemium | Pay-as-you-go | Free tier with limited usage - 30 free minutes then $0.05/min |
| Subscription | Annual | Paid tier removing caps - $100/month with full feature access |
| Subscription | Multi-year contract | Custom enterprise pricing for massive scale deployments |
Go-to-market motion3 records
Distribution channels6 records
Marketing channels7 records
Ultravox product offering
Product offeringCore offering
Ultravox operates the Ultravox Realtime platform, a speech-native voice AI infrastructure layer that processes audio directly without transcription, enabling developers and enterprises to build real-time conversational voice agents. The platform exposes REST APIs, WebSockets, and SDKs across web and mobile (JavaScript, Python, React Native, Swift, Kotlin, Flutter), integrates with major telephony providers, supports retrieval-augmented generation via Ultravox Corpus, and offers voice cloning with multiple TTS providers. The proprietary Ultravox v0.7 model powers the platform, delivering ~900ms end-to-end latency and state-of-the-art benchmark performance.
Product overview
Ultravox is a research lab and product company offering the Ultravox Realtime platform — a speech-native voice AI infrastructure layer built on the Ultravox v0.7 model (powered by GLM 4.6). Unlike traditional voice AI systems that transcribe speech to text before LLM processing, Ultravox performs inference directly on audio, preserving paralinguistic cues and delivering ~900ms end-to-end latency. The platform is accessed via REST API, WebSockets, and SDKs (JavaScript, Python, React Native, Swift, Kotlin, Flutter). It integrates telephony providers (Twilio, Voximplant, Telnyx, Plivo, jambonz) and voice providers (Inworld, ElevenLabs, Cartesia, LMNT, Google, Respeecher). The Ultravox Corpus service enables RAG-based knowledge retrieval. Voice cloning is available for custom synthetic voices. Pricing spans Pay As You Go ($0.05/min), Pro ($100/month), and Enterprise (custom).
Differentiator
Problem solved
Functional benefit
Brands
- Ultravox Realtime Platform: Developer-friendly real-time voice AI platform with APIs, SDKs, and agentic-ready primitives for building conversational voice AI experiences.
- Ultravox v0.7
- UltraVox VAD v0.1
Products and services
- Ultravox Realtime Platform The core voice AI platform enabling developers and enterprises to build real-time speech-native voice agents. Provides a unified stack combining speech understanding, reasoning, and speech generation without transcription, delivered with ~900ms end-to-end latency.
- Ultravox v0.7 Speech Model State-of-the-art speech-native model using GLM 4.6 (355B parameters, 160 experts per layer) as its LLM backbone. Achieves 91.8% on Big Bench Audio without reasoning and 97% with thinking enabled; performs inference directly on audio without transcription. Released as open weights on Hugging Face.
- Ultravox Voice API REST API underlying the Ultravox Realtime platform with endpoints for accounts, agents, calls, voices, corpora, tools, webhooks, SIP configuration, and telephony credentials. Supports WebSocket-based real-time streaming and webhook events for call.started and call.ended.
- Ultravox Client SDKs Client software development kits enabling developers to integrate Ultravox voice AI into web and mobile applications. Available for JavaScript/TypeScript, Python, React Native, Swift (iOS), Kotlin (Android), and Flutter.
- Ultravox Realtime Telephony Telephony module enabling voice agents to make and receive phone calls via SIP trunking, with built-in integrations for Twilio, Voximplant, Telnyx, Plivo, and jambonz. Supports inbound/outbound calls, SIP call transfers (cold and warm), IVR flow handling, and outbound call scheduling.
- Ultravox Corpus (RAG) Retrieval-augmented generation knowledge base service integrated into Ultravox Realtime. Users upload documents, websites, or other content to create corpora that voice agents query during conversations, with isolation between customers' knowledge bases. Up to 20 corpora on the Pro plan.
Quantifiable outcome
- 91.8% on Big Bench Audio (97% with thinking) - highest score among speech models
- +4 more outcomes
Companies that use Ultravox
Customer profileNamed customers1 record
Segments4 records
Ideal customer profiles4 records
Ultravox technology and API
TechnologyTechnology focussed Yes
API detail
- Has API
- Yes
- API docs
- API detail
Core technology
AI maturity
App detail
Integration8 records
AI capability7 records
Feature8 records
Ultravox partnerships and signals
Strategic signalPartnerships
Five partnerships are on record, tiered core.
- InworldcoreIntegration of Inworld TTS 1.5 voices into Ultravox Realtime platform. Users can build voice agents using Inworld's pre-built voices in 15 languages or custom voice clones. Joint promotional credit offer of up to $100 for customers using Inworld voices (January 21 - February 28, 2026).
- PipecatcoreUltravox Realtime available as speech-to-speech service in Pipecat voice AI framework. Ultravox v0.7 demonstrated superior performance in Pipecat team's independent benchmark, outperforming all other speech-to-speech models tested. Designed as drop-in replacement.
- VoximplantcoreNative integration enabling SIP calling through Voximplant platform. Voximplant provides hosted telephony platform that connects to Ultravox via WebSockets, managing connections with existing SIP telephony infrastructure. Includes ready-to-use scenarios for incoming and outgoing calls.
- TwiliocoreTelephony integration allowing AI agents to handle calls via Twilio. Built-in coldTransfer and warmTransfer tools work with Twilio for call handoffs to human operators. Complete working examples available in ultravox-examples GitHub repo.
- Hugging FacecoreOpen weight model releases published on Hugging Face. Model weights for Ultravox v0.7 (GLM 4.6 backbone) and previous versions available for download. Supports open science philosophy and community research.
Scale indicators9 records
Recent moves5 records
Expansion highlights7 records
Ultravox competitors and assessment
Company assessmentDirect peers
- Retell AI: Retell AI provides a voice agent platform with low-latency conversational AI for enterprise customer service and sales. It targets an overlapping enterprise segment with similar telephony integration (Twilio, etc.) and developer-first API access, competing for the same voice AI agent budget.
- AssemblyAI: AssemblyAI provides speech recognition and audio intelligence APIs with a Universal-1 model and emerging real-time/agentic features. It targets the same developer customer as Ultravox with usage-based pricing and a model-plus-API stack, competing for voice AI infrastructure spend.
- Vapi: Vapi is a developer platform for building, testing, and deploying voice AI agents with telephony integrations. It targets an overlapping developer/enterprise customer base as Ultravox and competes in the same voice agent infrastructure layer, though Vapi leans orchestration while Ultravox leans speech-native model.
- Deepgram: Deepgram provides speech-to-text and increasingly speech-to-speech voice AI APIs for developers. It targets the same developer-first, usage-priced customer base as Ultravox, with similar SDK and enterprise motions, though Deepgram has historically focused on STT accuracy rather than speech-native reasoning.
- ElevenLabs: ElevenLabs is a leading voice AI platform spanning TTS, voice cloning, and conversational agents. It is listed as one of Ultravox's supported TTS providers (Inworld, ElevenLabs, Cartesia, etc.) and competes head-on in the developer/enterprise voice agent space, particularly for high-quality voice output.
Broad incumbents
- OpenAI (Realtime API): OpenAI's Realtime API offers speech-to-speech conversations via GPT-4o Realtime. It is a direct competitor to Ultravox in low-latency voice agents, with substantially more resources and bundled distribution, but Ultravox differentiates on accuracy (97.7% vs 86.7% on AIEWF) and latency (0.864s vs 1.536s).
- Google (Gemini Live / Vertex AI Speech): Google's Gemini Live provides a multimodal live voice experience and competes directly with Ultravox's real-time speech-to-speech platform. Ultravox outperforms Gemini Live on AIEWF (97.7% vs 86.0%) and latency (0.864s vs 2.624s), but Google has unmatched cloud distribution.
Emerging players
- Hume AI: Hume AI offers an emotionally intelligent voice AI API (Empathic Voice Interface) that captures emotional and paralinguistic signals. It competes with Ultravox on the dimension Ultravox emphasizes (non-transcript-based, emotion-aware voice), and targets similar enterprise conversational AI buyers.
- Cartesia: Cartesia builds real-time speech models with a focus on state-space model (SSM) architecture for low-latency voice AI. It is listed as a supported TTS provider on Ultravox and overlaps as an emerging speech-native model competitor targeting similar enterprise/developer use cases.
Others
- Pipecat (Daily): Pipecat is an open-source voice AI orchestration framework that integrates Ultravox as a drop-in speech-to-speech service. While not a direct competitor, Pipecat sits in the same developer stack and its independent benchmark showcasing Ultravox v0.7 makes it a key ecosystem partner that drives developer adoption of Ultravox over GPT Realtime or Gemini Live.
Market position
Strengths5 records
Weaknesses5 records
Competitive moat6 records
Key risks6 records
Key highlights7 records
Customer concentration
Ultravox social profiles
Digital presenceUltravox compliance and trust
Trust signalCompliance1 record
Ultravox financial estimates
Financial estimateRevenue estimate
Valuation estimate
Ultravox leadership team
Management profileNumber of profiles
Profiles7 records
Ultravox funding detail
Funding detailFunding overview
Funding rounds3 records
Investors6 records
Funding detail is available on the Subscription and Enterprise plan.Contact sales →
Ultravox M&A and investment
M&A and investmentM&A
Investments
M&A and investment is available on the Subscription and Enterprise plan.Contact sales →
Frequently asked questions about Ultravox
What does Ultravox do?
Ultravox operates the Ultravox Realtime platform, a speech-native voice AI infrastructure layer that processes audio directly without transcription, enabling developers and enterprises to build real-time conversational voice agents. The platform exposes REST APIs, WebSockets, and SDKs across web and mobile (JavaScript, Python, React Native, Swift, Kotlin, Flutter), integrates with major telephony providers, supports retrieval-augmented generation via Ultravox Corpus, and offers voice cloning with multiple TTS providers. The proprietary Ultravox v0.7 model powers the platform, delivering ~900ms end-to-end latency and state-of-the-art benchmark performance.
Is Ultravox a public or private company?
Ultravox is a private company. It is classified as venture growth investor backed and is currently operating.
When was Ultravox founded?
Ultravox was founded in 2023. It employs 11 to 50 people.
Where is Ultravox based?
Ultravox is headquartered in Seattle, United States, in the North America region.
How does Ultravox make money?
Five revenue lines are on record. Usage-based Voice AI (Pay As You Go) is the primary driver. The others are pro Subscription, enterprise Custom, SIP Telephony and threads (Token-based).
Who are Ultravox's main competitors?
Direct peers on record are Retell AI, AssemblyAI, Vapi, Deepgram and ElevenLabs. Broad incumbents are OpenAI (Realtime API) and Google (Gemini Live / Vertex AI Speech). Emerging players are Hume AI and Cartesia. Pipecat (Daily) is listed as an others.
Does Ultravox have an API?
Yes. REST API for building and managing voice AI agents, with endpoints covering agents, calls, voices, corpora (RAG), tools, webhooks, SIP telephony, and Twilio/Telnyx/Plivo configuration. Also supports WebSocket-based real-time streaming. SDKs available in JavaScript/TypeScript, Python, React Native, Swift, Kotlin, and Flutter. Webhook support for call.started and call.ended events. Developer documentation is at docs.ultravox.ai.
What industry is Ultravox in?
Ultravox's product category is Voice AI Platform. Its primary akta.pro industry code is HDAAAFAD, Voice Assistants & Voice UI (VUI). Its NAICS code is 54151 and its SIC code is 7371.