Realtime Speech-to-Text API

Real-time transcription your notetaker, agents, and captions can depend on

Universal-3 Pro Streaming

Your transcriptions will show here...

import assemblyai as aai
from assemblyai.streaming.v3 import (
    StreamingClient,
    StreamingClientOptions,
    StreamingEvents,
    StreamingParameters,
    TurnEvent,
)

def on_turn(self, event: TurnEvent):
    print(f"{event.transcript} ({event.end_of_turn})")

client = StreamingClient(
    StreamingClientOptions(
        api_key=API_KEY,
        api_host="streaming.assemblyai.com",
    )
)

client.on(StreamingEvents.Turn, on_turn)

client.connect(
    StreamingParameters(
        speech_model="u3-rt-pro",
        sample_rate=16000,
        continuous_partials=True,
    )
)

try:
    client.stream(aai.extras.MicrophoneStream(sample_rate=16000))
finally:
    client.disconnect(terminate=True)

Models

Pick the model that fits your workload

Real-time transcription fast enough for voice agents, accurate enough for production.

Universal-3 Pro Streaming

The most accurate, controllable model on the market.

$0.45 / hr

Learn more

Best for: voice agents and real-time assistants

EN, ES, FR, DE, IT, PT

~150ms P50 latency, finals-only output

Highest accuracy on names, numbers, and technical terms

Universal Streaming

Production-grade streaming accuracy at the lowest price.

$0.15 / hr

Learn more

Best for: live captioning, meetings, agent assist

English Only

Partial and final transcripts

Production-grade accuracy at the lowest price

Universal Streaming Multilingual

Global contact centers and multilingual voice experiences.

$0.15 / hr

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Best for: High volume, multilingual use cases

EN, ES, FR, DE, IT, PT

Language detection

Partial and final transcripts

Add-on

Medical Mode

Clinical-grade streaming accuracy

Clinical-grade accuracy
Medical terminology recognition
Noise-resilient transcription
HIPAA-ready infrastructure

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Compare features

Model

U-3 Pro Streaming Voice agents, AI scribes

Universal Streaming AI notetakers, call centers

Univ. Multilingual Global contact centers

Price

$0.45 /hr

$0.15 /hr

Languages

EN, ES, FR, DE, IT, PT

English

EN, ES, FR, DE, IT, PT

Natural language prompting

Up to ~1,500 words

—

Keyterm prompting

Up to ~100 words

Code-switching

—

Speaker diarization

10+ speakers

Medical terminology

Medical mode add-on

HIPAA BAA

On request

Unlimited concurrency

Use cases

Built for every voice workflow

Real-time transcription powers every application where you stream audio.

Voice Agents

Production-grade transcription for voice agents, available standalone or through our Voice Agent API. Drops into Pipecat, LiveKit, or your own stack.

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AI Notetaker

Capture patient-provider conversations in real time with clinical-grade accuracy.

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Conversation Intelligence, and Call Analytics

Stream live transcripts from every sales call, support ticket, and customer interaction.

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AI Scribes

Capture patient-provider conversations in real time with clinical-grade accuracy.

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Agent Assist

Real-time transcription that surfaces the right answer to agents mid-call.

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Dictation, and Voice Input

Power voice input in productivity tools, mobile apps, and accessibility workflows.

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Playground

We’re not playing around, but you can

Put our Voice AI models to the test in our no-code playground.

Try it out

Common questions

: The Realtime Speech-to-Text API transcribes live audio as it's spoken. You send audio over a secure WebSocket to the API, which returns transcripts within a few hundred milliseconds (~300 ms P50).
: Yes. AssemblyAI scales automatically with no hard caps on concurrent streams. You can run as many simultaneous transcription sessions as your application requires.
: Create a free account, connect to the WebSocket endpoint, set your sample rate, stream audio chunks, and handle transcript events. Our SDKs for Python and JavaScript make it a few lines of code.
: Universal Streaming is $0.15 per hour. Universal-3 Pro Streaming is $0.45 per hour. Billing is based on total session duration.
: Immutable transcripts, intelligent endpointing, word-level timestamps, keyterms prompting, speaker diarization, and unlimited concurrent streams.
: English is supported by default. Universal Streaming Multilingual supports Spanish, French, German, Italian, and Portuguese.