--- title: AssemblyAI Universal-3 Pro description: AssemblyAI's Universal 3 Pro speech recognition model for high-accuracy transcription. image: https://developers.cloudflare.com/dev-products-preview.png --- > Documentation Index > Fetch the complete documentation index at: https://developers.cloudflare.com/ai/llms.txt > Use this file to discover all available pages before exploring further. [Skip to content](#%5Ftop) ![AssemblyAI logo](https://developers.cloudflare.com/_astro/assemblyai.DKrad3Z3.svg) # AssemblyAI Universal-3 Pro Automatic Speech Recognition • AssemblyAI `assemblyai/universal-3-pro` AssemblyAI's Universal 3 Pro speech recognition model for high-accuracy transcription. | Model Info | | | ------------------- | ---------------------------------------------------------------------------------------------------------------------------- | | Terms and License | [link ↗](https://www.assemblyai.com/legal/terms-of-service) | | More information | [link ↗](https://www.assemblyai.com/) | | Zero data retention | Yes | | Pricing | [View pricing in the Cloudflare dashboard ↗](https://dash.cloudflare.com/?to=/:account/ai/models/assemblyai/universal-3-pro) | ## Usage * [ TypeScript ](#tab-panel-310) * [ cURL ](#tab-panel-311) TypeScript ``` const response = await env.AI.run( 'assemblyai/universal-3-pro', { audio_url: 'https://cdn.openai.com/API/docs/audio/alloy.wav' },)console.log(response) ``` Terminal window ``` curl https://api.cloudflare.com/client/v4/accounts/$CLOUDFLARE_ACCOUNT_ID/ai/run \ --header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \ --header "Content-Type: application/json" \ --data '{ "model": "assemblyai/universal-3-pro", "input": { "audio_url": "https://cdn.openai.com/API/docs/audio/alloy.wav" }}' ``` * [ Output ](#tab-panel-318) * [ Raw response ](#tab-panel-319) The sun rises in the east and sets in the west. This simple fact has been observed by humans for thousands of years. ``` { "gatewayMetadata": { "keySource": "Unified" }, "result": { "confidence": 0.99276465, "language_code": "en", "language_confidence": 0.9998, "text": "The sun rises in the east and sets in the west. This simple fact has been observed by humans for thousands of years.", "utterances": null, "words": [ { "confidence": 0.9713957, "end": 129, "speaker": null, "start": 32, "text": "The" }, { "confidence": 0.97053415, "end": 404, "speaker": null, "start": 129, "text": "sun" }, { "confidence": 0.9998932, "end": 809, "speaker": null, "start": 420, "text": "rises" }, { "confidence": 0.999092, "end": 922, "speaker": null, "start": 841, "text": "in" }, { "confidence": 0.9997658, "end": 1068, "speaker": null, "start": 922, "text": "the" }, { "confidence": 0.9684294, "end": 1456, "speaker": null, "start": 1149, "text": "east" }, { "confidence": 0.9894344, "end": 1634, "speaker": null, "start": 1570, "text": "and" }, { "confidence": 0.9999058, "end": 2055, "speaker": null, "start": 1715, "text": "sets" }, { "confidence": 0.9997663, "end": 2104, "speaker": null, "start": 2055, "text": "in" }, { "confidence": 0.9999552, "end": 2217, "speaker": null, "start": 2120, "text": "the" }, { "confidence": 0.9913442, "end": 2638, "speaker": null, "start": 2217, "text": "west." }, { "confidence": 0.9974367, "end": 3221, "speaker": null, "start": 3107, "text": "This" }, { "confidence": 0.99965656, "end": 3560, "speaker": null, "start": 3269, "text": "simple" }, { "confidence": 0.999713, "end": 3997, "speaker": null, "start": 3593, "text": "fact" }, { "confidence": 0.99924207, "end": 4175, "speaker": null, "start": 3997, "text": "has" }, { "confidence": 0.9995851, "end": 4289, "speaker": null, "start": 4224, "text": "been" }, { "confidence": 0.9984724, "end": 4807, "speaker": null, "start": 4337, "text": "observed" }, { "confidence": 0.9997143, "end": 4952, "speaker": null, "start": 4807, "text": "by" }, { "confidence": 0.9997894, "end": 5422, "speaker": null, "start": 4969, "text": "humans" }, { "confidence": 0.99947494, "end": 5519, "speaker": null, "start": 5422, "text": "for" }, { "confidence": 0.99950385, "end": 6118, "speaker": null, "start": 5616, "text": "thousands" }, { "confidence": 0.9995235, "end": 6231, "speaker": null, "start": 6118, "text": "of" }, { "confidence": 0.9519594, "end": 6636, "speaker": null, "start": 6328, "text": "years." } ] }, "state": "Completed"} ``` ## Examples **With Language Code** — Transcribe with an explicit language code * [ TypeScript ](#tab-panel-312) * [ cURL ](#tab-panel-313) TypeScript ``` const response = await env.AI.run( 'assemblyai/universal-3-pro', { audio_url: 'https://cdn.openai.com/API/docs/audio/echo.wav', language_code: 'en' },)console.log(response) ``` Terminal window ``` curl https://api.cloudflare.com/client/v4/accounts/$CLOUDFLARE_ACCOUNT_ID/ai/run \ --header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \ --header "Content-Type: application/json" \ --data '{ "model": "assemblyai/universal-3-pro", "input": { "audio_url": "https://cdn.openai.com/API/docs/audio/echo.wav", "language_code": "en" }}' ``` * [ Output ](#tab-panel-322) * [ Raw response ](#tab-panel-323) In the heart of the city, there is a large park where people go to relax and enjoy nature. The park has a beautiful pond with ducks and swans. ``` { "gatewayMetadata": { "keySource": "Unified" }, "result": { "confidence": 0.9927905, "language_code": "en_us", "language_confidence": null, "text": "In the heart of the city, there is a large park where people go to relax and enjoy nature. The park has a beautiful pond with ducks and swans.", "utterances": null, "words": [ { "confidence": 0.88134426, "end": 80, "speaker": null, "start": 32, "text": "In" }, { "confidence": 0.9984907, "end": 241, "speaker": null, "start": 177, "text": "the" }, { "confidence": 0.99956447, "end": 500, "speaker": null, "start": 258, "text": "heart" }, { "confidence": 0.9995684, "end": 548, "speaker": null, "start": 500, "text": "of" }, { "confidence": 0.99977916, "end": 677, "speaker": null, "start": 596, "text": "the" }, { "confidence": 0.9956655, "end": 967, "speaker": null, "start": 677, "text": "city," }, { "confidence": 0.9987048, "end": 1435, "speaker": null, "start": 1322, "text": "there" }, { "confidence": 0.99971443, "end": 1516, "speaker": null, "start": 1467, "text": "is" }, { "confidence": 0.99948585, "end": 1596, "speaker": null, "start": 1564, "text": "a" }, { "confidence": 0.9987669, "end": 2016, "speaker": null, "start": 1709, "text": "large" }, { "confidence": 0.9981509, "end": 2467, "speaker": null, "start": 2129, "text": "park" }, { "confidence": 0.9559358, "end": 2838, "speaker": null, "start": 2693, "text": "where" }, { "confidence": 0.99979085, "end": 3145, "speaker": null, "start": 2854, "text": "people" }, { "confidence": 0.9993555, "end": 3338, "speaker": null, "start": 3177, "text": "go" }, { "confidence": 0.9998317, "end": 3467, "speaker": null, "start": 3338, "text": "to" }, { "confidence": 0.99991953, "end": 4064, "speaker": null, "start": 3500, "text": "relax" }, { "confidence": 0.9988979, "end": 4161, "speaker": null, "start": 4064, "text": "and" }, { "confidence": 0.9999237, "end": 4484, "speaker": null, "start": 4161, "text": "enjoy" }, { "confidence": 0.998528, "end": 4887, "speaker": null, "start": 4484, "text": "nature." }, { "confidence": 0.990198, "end": 5758, "speaker": null, "start": 5597, "text": "The" }, { "confidence": 0.99979144, "end": 6016, "speaker": null, "start": 5758, "text": "park" }, { "confidence": 0.99926263, "end": 6177, "speaker": null, "start": 6064, "text": "has" }, { "confidence": 0.9992211, "end": 6242, "speaker": null, "start": 6177, "text": "a" }, { "confidence": 0.99989605, "end": 6774, "speaker": null, "start": 6322, "text": "beautiful" }, { "confidence": 0.9998628, "end": 7193, "speaker": null, "start": 6790, "text": "pond" }, { "confidence": 0.99960047, "end": 7355, "speaker": null, "start": 7193, "text": "with" }, { "confidence": 0.99963534, "end": 7806, "speaker": null, "start": 7371, "text": "ducks" }, { "confidence": 0.99866796, "end": 7919, "speaker": null, "start": 7855, "text": "and" }, { "confidence": 0.9833702, "end": 8629, "speaker": null, "start": 7935, "text": "swans." } ] }, "state": "Completed"} ``` **With Key Terms** — Improve accuracy for domain-specific vocabulary * [ TypeScript ](#tab-panel-316) * [ cURL ](#tab-panel-317) TypeScript ``` const response = await env.AI.run( 'assemblyai/universal-3-pro', { audio_url: 'https://cdn.openai.com/API/docs/audio/nova.wav', keyterms_prompt: ['Kubernetes', 'microservices', 'containerization', 'load balancer'], },)console.log(response) ``` Terminal window ``` curl https://api.cloudflare.com/client/v4/accounts/$CLOUDFLARE_ACCOUNT_ID/ai/run \ --header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \ --header "Content-Type: application/json" \ --data '{ "model": "assemblyai/universal-3-pro", "input": { "audio_url": "https://cdn.openai.com/API/docs/audio/nova.wav", "keyterms_prompt": [ "Kubernetes", "microservices", "containerization", "load balancer" ] }}' ``` * [ Output ](#tab-panel-324) * [ Raw response ](#tab-panel-325) In the kitchen, the aroma of freshly baked bread filled the air. The loaves were golden brown and crusty on the outside and soft and warm on the inside. ``` { "gatewayMetadata": { "keySource": "Unified" }, "result": { "confidence": 0.9901139, "language_code": "en", "language_confidence": 0.9969, "text": "In the kitchen, the aroma of freshly baked bread filled the air. The loaves were golden brown and crusty on the outside and soft and warm on the inside.", "utterances": null, "words": [ { "confidence": 0.9785539, "end": 80, "speaker": null, "start": 32, "text": "In" }, { "confidence": 0.99962807, "end": 242, "speaker": null, "start": 177, "text": "the" }, { "confidence": 0.99617165, "end": 565, "speaker": null, "start": 258, "text": "kitchen," }, { "confidence": 0.9991928, "end": 839, "speaker": null, "start": 743, "text": "the" }, { "confidence": 0.99992657, "end": 1292, "speaker": null, "start": 839, "text": "aroma" }, { "confidence": 0.99955577, "end": 1405, "speaker": null, "start": 1308, "text": "of" }, { "confidence": 0.9996594, "end": 1889, "speaker": null, "start": 1405, "text": "freshly" }, { "confidence": 0.99850214, "end": 2261, "speaker": null, "start": 1970, "text": "baked" }, { "confidence": 0.9999217, "end": 2584, "speaker": null, "start": 2293, "text": "bread" }, { "confidence": 0.9999, "end": 2859, "speaker": null, "start": 2600, "text": "filled" }, { "confidence": 0.99993885, "end": 3004, "speaker": null, "start": 2859, "text": "the" }, { "confidence": 0.9961201, "end": 3262, "speaker": null, "start": 3020, "text": "air." }, { "confidence": 0.99501073, "end": 4119, "speaker": null, "start": 4054, "text": "The" }, { "confidence": 0.9997483, "end": 4522, "speaker": null, "start": 4215, "text": "loaves" }, { "confidence": 0.9998282, "end": 4781, "speaker": null, "start": 4619, "text": "were" }, { "confidence": 0.99248224, "end": 5249, "speaker": null, "start": 4878, "text": "golden" }, { "confidence": 0.9700398, "end": 5718, "speaker": null, "start": 5362, "text": "brown" }, { "confidence": 0.9419883, "end": 5992, "speaker": null, "start": 5928, "text": "and" }, { "confidence": 0.9994146, "end": 6541, "speaker": null, "start": 6089, "text": "crusty" }, { "confidence": 0.9997141, "end": 6703, "speaker": null, "start": 6574, "text": "on" }, { "confidence": 0.9999218, "end": 6784, "speaker": null, "start": 6719, "text": "the" }, { "confidence": 0.9993179, "end": 7365, "speaker": null, "start": 6881, "text": "outside" }, { "confidence": 0.8661144, "end": 7462, "speaker": null, "start": 7365, "text": "and" }, { "confidence": 0.9996922, "end": 7882, "speaker": null, "start": 7462, "text": "soft" }, { "confidence": 0.9998481, "end": 7995, "speaker": null, "start": 7882, "text": "and" }, { "confidence": 0.99996424, "end": 8270, "speaker": null, "start": 8028, "text": "warm" }, { "confidence": 0.9998791, "end": 8399, "speaker": null, "start": 8270, "text": "on" }, { "confidence": 0.99982506, "end": 8512, "speaker": null, "start": 8415, "text": "the" }, { "confidence": 0.9834439, "end": 8964, "speaker": null, "start": 8512, "text": "inside." } ] }, "state": "Completed"} ``` **Speaker Diarization** — Identify different speakers in the audio * [ TypeScript ](#tab-panel-314) * [ cURL ](#tab-panel-315) TypeScript ``` const response = await env.AI.run( 'assemblyai/universal-3-pro', { audio_url: 'https://cdn.openai.com/API/docs/audio/onyx.wav', speaker_labels: true },)console.log(response) ``` Terminal window ``` curl https://api.cloudflare.com/client/v4/accounts/$CLOUDFLARE_ACCOUNT_ID/ai/run \ --header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \ --header "Content-Type: application/json" \ --data '{ "model": "assemblyai/universal-3-pro", "input": { "audio_url": "https://cdn.openai.com/API/docs/audio/onyx.wav", "speaker_labels": true }}' ``` * [ Output ](#tab-panel-320) * [ Raw response ](#tab-panel-321) The train chugged along the tracks, carrying passengers to their destinations. The rhythmic sound of the wheels on the rails was soothing. ``` { "gatewayMetadata": { "keySource": "Unified" }, "result": { "confidence": 0.99781793, "language_code": "en", "language_confidence": 0.9906, "text": "The train chugged along the tracks, carrying passengers to their destinations. The rhythmic sound of the wheels on the rails was soothing.", "utterances": [ { "confidence": 0.99781793, "end": 7719, "speaker": "A", "start": 32, "text": "The train chugged along the tracks, carrying passengers to their destinations. The rhythmic sound of the wheels on the rails was soothing." } ], "words": [ { "confidence": 0.9742124, "end": 113, "speaker": "A", "start": 32, "text": "The" }, { "confidence": 0.99997795, "end": 403, "speaker": "A", "start": 177, "text": "train" }, { "confidence": 0.99713653, "end": 904, "speaker": "A", "start": 516, "text": "chugged" }, { "confidence": 0.9999881, "end": 1130, "speaker": "A", "start": 904, "text": "along" }, { "confidence": 0.9999676, "end": 1308, "speaker": "A", "start": 1227, "text": "the" }, { "confidence": 0.9995983, "end": 1808, "speaker": "A", "start": 1308, "text": "tracks," }, { "confidence": 0.9998933, "end": 2341, "speaker": "A", "start": 2131, "text": "carrying" }, { "confidence": 0.999992, "end": 3068, "speaker": "A", "start": 2454, "text": "passengers" }, { "confidence": 0.99999034, "end": 3229, "speaker": "A", "start": 3100, "text": "to" }, { "confidence": 0.9999908, "end": 3423, "speaker": "A", "start": 3262, "text": "their" }, { "confidence": 0.9992286, "end": 4198, "speaker": "A", "start": 3423, "text": "destinations." }, { "confidence": 0.99871373, "end": 5119, "speaker": "A", "start": 5038, "text": "The" }, { "confidence": 0.9999517, "end": 5523, "speaker": "A", "start": 5184, "text": "rhythmic" }, { "confidence": 0.99993813, "end": 5926, "speaker": "A", "start": 5523, "text": "sound" }, { "confidence": 0.99991894, "end": 6007, "speaker": "A", "start": 5926, "text": "of" }, { "confidence": 0.99993825, "end": 6088, "speaker": "A", "start": 6007, "text": "the" }, { "confidence": 0.99995935, "end": 6459, "speaker": "A", "start": 6169, "text": "wheels" }, { "confidence": 0.99997675, "end": 6605, "speaker": "A", "start": 6556, "text": "on" }, { "confidence": 0.99999475, "end": 6718, "speaker": "A", "start": 6637, "text": "the" }, { "confidence": 0.9999932, "end": 7105, "speaker": "A", "start": 6718, "text": "rails" }, { "confidence": 0.999851, "end": 7299, "speaker": "A", "start": 7138, "text": "was" }, { "confidence": 0.98378325, "end": 7719, "speaker": "A", "start": 7299, "text": "soothing." } ] }, "state": "Completed"} ``` ## Parameters * [ Input ](#tab-panel-326) * [ Output ](#tab-panel-327) audio\_url `string`The URL of the audio file to transcribe. Can be a publicly accessible URL or a data URI (data:audio/...;base64,...). For data URIs, the audio will be uploaded to AssemblyAI automatically. Required for pre-recorded transcription (when stream is false or not set). websocket `boolean`Enable real-time WebSocket streaming for live audio transcription. When true, a WebSocket connection is established instead of submitting a pre-recorded transcription job. Cannot be used with audio\_url. language\_code `string`The language code for the audio file (e.g., "en", "es", "fr"). Defaults to automatic language detection. language\_detection `boolean`Enable automatic language detection. When enabled with speech\_models, the system will automatically select the best model for the detected language. prompt `string`A custom prompt to guide transcription style, formatting, and output characteristics. Maximum 1,500 words. ▶keyterms\_prompt\[\] `array`An array of up to 1,000 words or phrases (max 6 words per phrase) to improve transcription accuracy. Cannot be used with the prompt parameter. temperature `number`minimum: 0maximum: 1Controls randomness in model output (0.0-1.0). Lower values make output more deterministic. Default is 0.0. speaker\_labels `boolean`Enable speaker diarization to identify different speakers in the audio. speakers\_expected `integer`minimum: 1maximum: 9007199254740991Expected number of speakers for speaker diarization. auto\_chapters `boolean`Enable automatic chapter detection. entity\_detection `boolean`Enable detection of entities like names, organizations, and locations. sentiment\_analysis `boolean`Enable sentiment analysis for each sentence. auto\_highlights `boolean`Enable automatic extraction of key phrases and highlights. content\_safety `boolean`Enable content safety detection for sensitive content. iab\_categories `boolean`Enable IAB (Interactive Advertising Bureau) content taxonomy classification. ▶custom\_spelling\[\] `array`Custom spelling rules to replace specific words or phrases in the transcription output. disfluencies `boolean`Include filler words like "um", "uh", etc. in the transcript. multichannel `boolean`Process each audio channel separately for multi-channel audio files. dual\_channel `boolean`Process audio as dual-channel (stereo) for better accuracy. webhook\_url `string`format: uriURL to receive webhook notifications when transcription is complete. audio\_start\_from `integer`minimum: 0maximum: 9007199254740991Timestamp (in milliseconds) to start transcription from. audio\_end\_at `integer`minimum: 0maximum: 9007199254740991Timestamp (in milliseconds) to end transcription at. ▶word\_boost\[\] `array`Array of words to boost recognition accuracy (legacy - use keyterms\_prompt instead). boost\_param `string`enum: low, default, highHow much to boost the words in word\_boost. filter\_profanity `boolean`Filter profanity from the transcription. redact\_pii `boolean`Redact personally identifiable information. redact\_pii\_audio `boolean`Generate a redacted audio file with PII removed. ▶redact\_pii\_policies\[\] `array`Specific PII policies to apply for redaction. redact\_pii\_sub `string`enum: entity\_name, hashStrategy for substituting redacted PII. speech\_threshold `number`minimum: 0maximum: 1Confidence threshold for speech detection. domain `string`enum: medical-v1Domain-specific transcription mode. "medical-v1" enables medical terminology optimization. text `string`The transcribed text. words `array | null`Word-level timestamps and confidence scores. utterances `array | null`Speaker-separated utterances (when speaker\_labels is enabled). confidence `number | null`Overall confidence score for the transcription. language\_code `string | null`Detected or specified language code. language\_confidence `number | null`Confidence score for language detection. ## API Schemas (Raw) Input [ ](https://developers.cloudflare.com/ai/models/assemblyai/universal-3-pro/schema-input.json "Open") [ ](https://developers.cloudflare.com/ai/models/assemblyai/universal-3-pro/schema-input.json "Download") Output [ ](https://developers.cloudflare.com/ai/models/assemblyai/universal-3-pro/schema-output.json "Open") [ ](https://developers.cloudflare.com/ai/models/assemblyai/universal-3-pro/schema-output.json "Download") ```json {"@context":"https://schema.org","@type":"TechArticle","@id":"https://developers.cloudflare.com/ai/models/assemblyai/universal-3-pro/#page","headline":"AssemblyAI Universal-3 Pro (AssemblyAI) · Cloudflare AI docs · Cloudflare AI docs","description":"AssemblyAI's Universal 3 Pro speech recognition model for high-accuracy transcription.","url":"https://developers.cloudflare.com/ai/models/assemblyai/universal-3-pro/","inLanguage":"en","image":"https://developers.cloudflare.com/dev-products-preview.png","publisher":{"@type":"Organization","name":"Cloudflare","url":"https://www.cloudflare.com/"},"isPartOf":{"@type":"WebSite","@id":"https://developers.cloudflare.com/#website","name":"Cloudflare Docs","url":"https://developers.cloudflare.com/"}} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/ai/","name":"AI"}},{"@type":"ListItem","position":3,"item":{"@id":"/ai/models/","name":"Models"}}]} ```