AssemblyAI: Universal-2

Name: Universal-2
Author: AssemblyAI

assemblyai/universal-2

active stt 1 provider

Playground

AssemblyAI high-accuracy, low-latency asynchronous transcription model with broad 99-language coverage.

AuthorAssemblyAI

Languagesmultilingual

Statusactive

Quick start

Universal-2

Create an API key

Create API key

Make a request

Pick an SDK, request mode, and language. The model and provider route are already filled in.

ElevenLabs SDK streaming STT

Streams microphone or file audio through the ElevenLabs-compatible allmodels route.

import { ElevenLabsClient } from "elevenlabs";

const client = new ElevenLabsClient({
  apiKey: process.env.ALLMODELS_API_KEY,
  baseUrl: "https://api.allmodels.io/el"
});

const connection = await client.speechToText.realtime.connect({
  modelId: "assemblyai/universal-2",
  languageCode: "en"
}, {
  queryParams: {
    provider: {
      "only": [
        "assemblyai"
      ]
    }
  }
});

// Send audio frames to connection, then handle transcript events.

Pass provider parameters

Pass provider preferences through the compatible SDK request options when you want to pin a route to a provider.

{
  queryParams: {
    provider: {
      only: ["assemblyai"]
    }
  }
}

Providers

Different providers can host the same model. Choose one provider when you need a fixed backend, or let routing select among them.

ProviderSlugPer hourLatencyiModesUptime

AssemblyAI 49 params

assemblyai

$0.15

—

Synchronous · Batch

AssemblyAI

49 documented provider parameters for this route.

Pricing

ModeLanguagePer hour

Async Any $0.15

+ Speaker Diarization Any $0.02

+ Medical Mode Any $0.15

+ PII Redaction Any $0.08

+ Entity Detection Any $0.08

+ Profanity Filtering Any $0.01

Parameters

audio_url body · string · required

The URL of the audio or video file to transcribe.

audio_end_at body · integer · optional

The point in time, in milliseconds, to stop transcribing in your media file. See [Set the start and end of the transcript](https://www.assemblyai.com/docs/pre-recorded-audio/set-the-start-and-end-of-the-transcript) for more details.

audio_start_from body · integer · optional

The point in time, in milliseconds, to begin transcribing in your media file. See [Set the start and end of the transcript](https://www.assemblyai.com/docs/pre-recorded-audio/set-the-start-and-end-of-the-transcript) for more details.

auto_chapters body · boolean · optional

Enable [Auto Chapters](https://www.assemblyai.com/docs/speech-understanding/auto-chapters), can be true or false. Deprecated - use [LLM Gateway](https://www.assemblyai.com/docs/llm-gateway/quickstart) instead for more flexible chapter summaries. See the [updated Auto Chapters page](https://www.assemblyai.com/docs/speech-understanding/auto-chapters) for details. Note: This parameter is only supported for the Universal-2 model.

default false

auto_highlights body · boolean · optional

Enable [Key Phrases](https://www.assemblyai.com/docs/speech-understanding/key-phrases), either true or false

default false

content_safety body · boolean · optional

Enable [Content Moderation](https://www.assemblyai.com/docs/content-moderation), can be true or false

default false

content_safety_confidence body · integer · optional

The confidence threshold for the [Content Moderation](https://www.assemblyai.com/docs/content-moderation) model. Values must be between 25 and 100.

default 50min 25max 100

custom_spelling body · array · optional

Customize how words are spelled and formatted using to and from values. See [Custom Spelling](https://www.assemblyai.com/docs/pre-recorded-audio/correct-spelling-of-terms) for more details.

custom_topics body · boolean · optional

This parameter does not currently have any functionality attached to it.

default false

disfluencies body · boolean · optional

Transcribe [Filler Words](https://www.assemblyai.com/docs/pre-recorded-audio/include-filler-words), like "umm", in your media file; can be true or false. Supported on Universal-3 Pro and Universal-2.

default false

domain body · string | null · optional

Enable domain-specific transcription models to improve accuracy for specialized terminology. Set to `"medical-v1"` to enable [Medical Mode](https://www.assemblyai.com/docs/pre-recorded-audio/medical-mode) for improved accuracy of medical terms such as medications, procedures, conditions, and dosages. Supported languages: English (`en`), Spanish (`es`), German (`de`), French (`fr`). If used with an unsupported language, the parameter is ignored and a warning is returned.

default null

entity_detection body · boolean · optional

Enable [Entity Detection](https://www.assemblyai.com/docs/speech-understanding/entity-detection), can be true or false

default false

filter_profanity body · boolean · optional

Filter profanity from the transcribed text, can be true or false. See [Profanity Filtering](https://www.assemblyai.com/docs/profanity-filtering) for more details.

default false

format_text body · boolean · optional

Enable [Text Formatting](https://www.assemblyai.com/docs/pre-recorded-audio), can be true or false

default true

iab_categories body · boolean · optional

Enable [Topic Detection](https://www.assemblyai.com/docs/speech-understanding/topic-detection), can be true or false

default false

keyterms_prompt body · array · optional

Improve accuracy with up to 200 (for Universal-2) or 1000 (for Universal-3 Pro) domain-specific words or phrases (maximum 6 words per phrase). See [Keyterms Prompting](https://www.assemblyai.com/docs/pre-recorded-audio/universal-3-pro/prompting#keyterms-prompting) for more details.

language_code body · string | string | null · optional

The language of your audio file. Possible values are found in [Supported Languages](https://www.assemblyai.com/docs/pre-recorded-audio/supported-languages). The default value is 'en_us'.

default "en_us"

language_codes body · array | null · optional

The language codes of your audio file. Used for [Code switching](/speech-to-text/pre-recorded-audio/code-switching) One of the values specified must be `en`.

language_confidence_threshold body · number · optional

The confidence threshold for the automatically detected language. An error will be returned if the language confidence is below this threshold. Defaults to 0. See [Automatic Language Detection](https://www.assemblyai.com/docs/pre-recorded-audio/language-detection) for more details.

default 0min 0max 1

language_detection body · boolean · optional

Enable [Automatic language detection](https://www.assemblyai.com/docs/pre-recorded-audio/language-detection), either true or false.

default false

language_detection_options body · object · optional

Specify options for [Automatic Language Detection](https://www.assemblyai.com/docs/pre-recorded-audio/language-detection).

multichannel body · boolean · optional

Enable [Multichannel](https://www.assemblyai.com/docs/pre-recorded-audio/transcribe-multiple-audio-channels) transcription, can be true or false.

default false

prompt body · string · optional

Provide natural language prompting of up to 1,500 words of contextual information to the model. See the [Prompting Guide](https://www.assemblyai.com/docs/pre-recorded-audio/prompting) for best practices. Note: This parameter is only supported for the Universal-3 Pro model.

punctuate body · boolean · optional

Enable [Automatic Punctuation](https://www.assemblyai.com/docs/pre-recorded-audio), can be true or false

default true

redact_pii body · boolean · optional

Redact PII from the transcribed text using the Redact PII model, can be true or false. See [PII Redaction](https://www.assemblyai.com/docs/pii-redaction) for more details.

default false

redact_pii_audio body · boolean · optional

Generate a copy of the original media file with spoken PII "beeped" out, can be true or false. See [PII redaction](https://www.assemblyai.com/docs/pii-redaction#request-for-redacted-audio) for more details.

default false

redact_pii_audio_options body · object · optional

Specify options for [PII redacted audio](https://www.assemblyai.com/docs/pii-redaction#request-for-redacted-audio) files.

redact_pii_audio_quality body · string · optional

Controls the filetype of the audio created by redact_pii_audio. Currently supports mp3 (default) and wav. See [PII redaction](https://www.assemblyai.com/docs/pii-redaction#request-for-redacted-audio) for more details.

2 enum values

Values

mp3wav

redact_pii_policies body · array · optional

The list of PII Redaction policies to enable. See [PII redaction](https://www.assemblyai.com/docs/pii-redaction) for more details.

redact_pii_return_unredacted body · boolean · optional

When set to `true`, returns the original unredacted transcript alongside the redacted one in the same response. Requires `redact_pii` to be `true`, otherwise a 400 error is returned. When enabled, the response includes the additional fields `unredacted_text`, `unredacted_words`, and `unredacted_utterances`. The existing `text`, `words`, and `utterances` fields remain fully redacted. When disabled (default), the response is unchanged and contains only the redacted transcript. See [PII redaction](https://www.assemblyai.com/docs/pii-redaction) for more details.

default false

redact_pii_sub body · string | null · optional

The replacement logic for detected PII, can be `entity_type` or `hash`. See [PII redaction](https://www.assemblyai.com/docs/pii-redaction) for more details.

default "hash"2 enum values

Values

entity_namehash

redact_static_entities body · object · optional

A map of user-defined terms to redact, where each key is a redaction label and each value is a list of exact terms to match (e.g. `{ "INTERNAL_TOOL": ["Bearclaw", "Cubclaw"] }`). Each matching term in the transcript is redacted using the `redact_pii_sub` substitution, on top of standard PII Redaction. Useful for redacting specific, predefined terms (proprietary names, internal codenames) that aren't general PII categories. This is a literal find-and-replace (tolerant of casing, surrounding punctuation, and minor spacing/hyphenation), not a model — it does not generalize beyond the terms you provide. Requires `redact_pii` to be `true`, otherwise a 400 error is returned. When `redact_pii_audio` is enabled, matched terms are also redacted in the audio output. See [Static Entity Redaction](https://www.assemblyai.com/docs/guardrails/redact-pii-from-transcripts#static-entity-redaction) for more details.

remove_audio_tags body · string | null · optional

Universal-3 Pro generates rich transcripts that can include inline annotations such as audio event markers and speaker cues. Set to `"all"` to remove all inline annotations, or `"speaker"` to remove only speaker cues while keeping other annotations. Note: This parameter is only supported for the Universal-3 Pro model.

default null2 enum values

Values

allspeaker

sentiment_analysis body · boolean · optional

Enable [Sentiment Analysis](https://www.assemblyai.com/docs/speech-understanding/sentiment-analysis), can be true or false

default false

speaker_labels body · boolean · optional

Enable [Speaker diarization](https://www.assemblyai.com/docs/pre-recorded-audio/label-speakers), can be true or false

default false

speaker_options body · object · optional

Specify options for [Speaker diarization](https://www.assemblyai.com/docs/pre-recorded-audio/label-speakers#set-a-range-of-possible-speakers). Use this to set a range of possible speakers.

speakers_expected body · integer | null · optional

Tells the speaker label model how many speakers it should attempt to identify. See [Set number of speakers expected](https://www.assemblyai.com/docs/pre-recorded-audio/label-speakers#set-number-of-speakers-expected) for more details.

default null

speech_model body · string | null · optional

This parameter has been replaced with the `speech_models` parameter, learn more about the `speech_models` parameter [here](https://www.assemblyai.com/docs/pre-recorded-audio/select-the-speech-model).

speech_models body · array · optional

Optional. List multiple speech models in priority order, allowing our system to automatically route your audio to the best available option. If omitted, defaults to `["universal-3-pro", "universal-2"]`. See [Model Selection](https://www.assemblyai.com/docs/pre-recorded-audio/select-the-speech-model) for available models and routing behavior.

default ["universal-3-pro","universal-2"]

speech_threshold body · number | null · optional

Reject audio files that contain less than this fraction of speech. Valid values are in the range [0, 1] inclusive. See [Speech Threshold](https://www.assemblyai.com/docs/speech-threshold) for more details.

default 0min 0max 1

speech_understanding body · object · optional

Enable speech understanding tasks like [Translation](https://www.assemblyai.com/docs/speech-understanding/translation), [Speaker Identification](https://www.assemblyai.com/docs/speech-understanding/speaker-identification), and [Custom Formatting](https://www.assemblyai.com/docs/speech-understanding/custom-formatting). See the task-specific docs for available options and configuration.

summarization body · boolean · optional

Enable [Summarization](https://www.assemblyai.com/docs/speech-understanding/summarization), can be true or false. Deprecated - use [LLM Gateway](https://www.assemblyai.com/docs/llm-gateway/quickstart) instead for more flexible summaries. See the [updated Summarization page](https://www.assemblyai.com/docs/speech-understanding/summarization) for details. Note: This parameter is only supported for the Universal-2 model.

default false

summary_model body · string · optional

The model to summarize the transcript

3 enum values

Values

informativeconversationalcatchy

summary_type body · string · optional

The type of summary

5 enum values

Values

bulletsbullets_verbosegistheadlineparagraph

temperature body · number · optional

Control the amount of randomness injected into the model's response. See the [Prompting Guide](https://www.assemblyai.com/docs/pre-recorded-audio/prompting) for more details. Note: This parameter can only be used with the Universal-3 Pro model.

default 0min 0max 1

topics body · array · optional

This parameter does not currently have any functionality attached to it.

webhook_auth_header_name body · string | null · optional

The header name to be sent with the transcript completed or failed [webhook](https://www.assemblyai.com/docs/deployment/webhooks-for-pre-recorded-audio) requests

default null

webhook_auth_header_value body · string | null · optional

The header value to send back with the transcript completed or failed [webhook](https://www.assemblyai.com/docs/deployment/webhooks-for-pre-recorded-audio) requests for added security

default null

webhook_url body · string · optional

The URL to which we send [webhook](https://www.assemblyai.com/docs/deployment/webhooks-for-pre-recorded-audio) requests.

Supported languages

No reviewed language list for this model yet.

Features

Speech to text

Transcribes spoken audio to text.

speech_to_text

Synchronous

Transcribes a fully-submitted audio file in a single synchronous request.

synchronous

Batch

AssemblyAI processes the request in a queue (submit, then poll for the transcript).

batch

Multilingual transcription

Supports 99 languages.

multilingual_transcription

Speaker diarization

Identifies and labels multiple speakers.

speaker_diarization

Word-level timestamps

Returns word-level timestamps.

word_timestamps

Code

ElevenLabs SDK streaming STT

Streams microphone or file audio through the ElevenLabs-compatible allmodels route.

import { ElevenLabsClient } from "elevenlabs";

const client = new ElevenLabsClient({
  apiKey: process.env.ALLMODELS_API_KEY,
  baseUrl: "https://api.allmodels.io/el"
});

const connection = await client.speechToText.realtime.connect({
  modelId: "assemblyai/universal-2",
  languageCode: "en"
}, {
  queryParams: {
    provider: {
      "only": [
        "assemblyai"
      ]
    }
  }
});

// Send audio frames to connection, then handle transcript events.