Grok STT

Model ID

Use with the Workers AI binding, the AI Gateway REST API, or the Unified API.

Calling the provider directly? Use the provider's model name instead, including with provider-native endpoints or the provider's own SDK. For example, Anthropic's name for anthropic/claude-opus-4.8 is claude-opus-4-8.

Third-party
Zero data retention

xAI's Grok speech-to-text model. Transcribes audio files into text across 25 languages with word-level timestamps, multichannel transcription, speaker diarization, and key-term biasing.

Model Info
Terms and License	link ↗
More information	link ↗
Zero data retention	Yes
Pricing	Per audio minute$0.001667 input audio minutes streaming$0.003334

Usage

const response = await env.AI.run(
  'xai/grok-stt',
  { url: 'https://storage.googleapis.com/cloud-samples-data/speech/brooklyn_bridge.mp3' },
)
console.log(response)

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": "xai/grok-stt",
  "input": {
    "url": "https://storage.googleapis.com/cloud-samples-data/speech/brooklyn_bridge.mp3"
  }
}'

How old is the Brooklyn Bridge?

{
  "state": "Completed",
  "result": {
    "text": "How old is the Brooklyn Bridge?",
    "language": "English",
    "duration": 1.85,
    "words": [
      {
        "text": "How",
        "start": 0.14,
        "end": 0.28
      },
      {
        "text": "old",
        "start": 0.4,
        "end": 0.6
      },
      {
        "text": "is",
        "start": 0.65,
        "end": 0.75
      },
      {
        "text": "the",
        "start": 0.81,
        "end": 0.89
      },
      {
        "text": "Brooklyn",
        "start": 0.95,
        "end": 1.29
      },
      {
        "text": "Bridge?",
        "start": 1.35,
        "end": 1.69
      }
    ]
  },
  "gatewayMetadata": {
    "keySource": "Unified"
  }
}

Examples

With Language and Formatting — Enable Inverse Text Normalization so spoken numbers become digits

const response = await env.AI.run(
  'xai/grok-stt',
  {
    url: 'https://storage.googleapis.com/cloud-samples-data/speech/brooklyn_bridge.mp3',
    language: 'en',
    format: true,
  },
)
console.log(response)

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": "xai/grok-stt",
  "input": {
    "url": "https://storage.googleapis.com/cloud-samples-data/speech/brooklyn_bridge.mp3",
    "language": "en",
    "format": true
  }
}'

How old is the Brooklyn Bridge?

{
  "state": "Completed",
  "result": {
    "text": "How old is the Brooklyn Bridge?",
    "language": "English",
    "duration": 1.85,
    "words": [
      {
        "text": "How",
        "start": 0.14,
        "end": 0.28
      },
      {
        "text": "old",
        "start": 0.4,
        "end": 0.6
      },
      {
        "text": "is",
        "start": 0.65,
        "end": 0.75
      },
      {
        "text": "the",
        "start": 0.81,
        "end": 0.89
      },
      {
        "text": "Brooklyn",
        "start": 0.95,
        "end": 1.29
      },
      {
        "text": "Bridge?",
        "start": 1.35,
        "end": 1.69
      }
    ]
  },
  "gatewayMetadata": {
    "keySource": "Unified"
  }
}

Speaker Diarization with Key Terms — Identify speakers and bias transcription toward proper nouns

const response = await env.AI.run(
  'xai/grok-stt',
  {
    url: 'https://storage.googleapis.com/cloud-samples-data/speech/brooklyn_bridge.mp3',
    language: 'en',
    diarize: true,
    keyterm: ['Brooklyn', 'Manhattan'],
  },
)
console.log(response)

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": "xai/grok-stt",
  "input": {
    "url": "https://storage.googleapis.com/cloud-samples-data/speech/brooklyn_bridge.mp3",
    "language": "en",
    "diarize": true,
    "keyterm": [
      "Brooklyn",
      "Manhattan"
    ]
  }
}'

How old is the Brooklyn Bridge?

{
  "state": "Completed",
  "result": {
    "text": "How old is the Brooklyn Bridge?",
    "language": "English",
    "duration": 1.85,
    "words": [
      {
        "text": "How",
        "start": 0.14,
        "end": 0.28,
        "speaker": 0
      },
      {
        "text": "old",
        "start": 0.4,
        "end": 0.6,
        "speaker": 0
      },
      {
        "text": "is",
        "start": 0.65,
        "end": 0.75,
        "speaker": 0
      },
      {
        "text": "the",
        "start": 0.81,
        "end": 0.89,
        "speaker": 0
      },
      {
        "text": "Brooklyn",
        "start": 0.95,
        "end": 1.29,
        "speaker": 0
      },
      {
        "text": "Bridge?",
        "start": 1.35,
        "end": 1.69,
        "speaker": 0
      }
    ]
  },
  "gatewayMetadata": {
    "keySource": "Unified"
  }
}

Filler Words Preserved — Keep filler words (uh, um, er) in the transcript instead of removing them

const response = await env.AI.run(
  'xai/grok-stt',
  {
    url: 'https://storage.googleapis.com/cloud-samples-data/speech/brooklyn_bridge.mp3',
    language: 'en',
    filler_words: true,
  },
)
console.log(response)

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": "xai/grok-stt",
  "input": {
    "url": "https://storage.googleapis.com/cloud-samples-data/speech/brooklyn_bridge.mp3",
    "language": "en",
    "filler_words": true
  }
}'

How old is the Brooklyn Bridge?

{
  "state": "Completed",
  "result": {
    "text": "How old is the Brooklyn Bridge?",
    "language": "English",
    "duration": 1.85,
    "words": [
      {
        "text": "How",
        "start": 0.14,
        "end": 0.28
      },
      {
        "text": "old",
        "start": 0.4,
        "end": 0.6
      },
      {
        "text": "is",
        "start": 0.65,
        "end": 0.75
      },
      {
        "text": "the",
        "start": 0.81,
        "end": 0.89
      },
      {
        "text": "Brooklyn",
        "start": 0.95,
        "end": 1.29
      },
      {
        "text": "Bridge?",
        "start": 1.35,
        "end": 1.69
      }
    ]
  },
  "gatewayMetadata": {
    "keySource": "Unified"
  }
}

Data URI Upload — Pass the audio file directly as a base64 data URI (mutually exclusive with `url`)

const response = await env.AI.run(
  'xai/grok-stt',
  { file: 'data:audio/wav;base64,<...>' },
)
console.log(response)

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": "xai/grok-stt",
  "input": {
    "file": "data:audio/wav;base64,<...>"
  }
}'

{
  "state": "Completed",
  "result": {
    "text": "",
    "language": "",
    "duration": 1
  },
  "gatewayMetadata": {
    "keySource": "Unified"
  }
}

Parameters

file

stringAudio file as a data URI (data:audio/...;base64,...) or an HTTPS URL the gateway fetches and uploads. Supported container formats: flac, mp3, mp4, m4a, mkv, ogg, opus, wav, aac. Raw formats (pcm, mulaw, alaw) also accepted — supply audio_format and sample_rate. Gateway-side size limit: 25 MB. Mutually exclusive with `url`.

url

stringformat: uriHTTPS URL of an audio file for xAI to fetch server-side. Mutually exclusive with `file` and `websocket`. No gateway-side size limit applies.

websocket

booleanEnable WebSocket streaming for speech-to-text. When true, establishes a bidirectional WebSocket connection for real-time audio transcription. Mutually exclusive with `file` and `url`.

audio_format

stringenum: pcm, mulaw, alawFormat hint for raw/headerless audio. Required for pcm, mulaw, alaw. Omit for container formats (mp3, wav, etc.) — xAI auto-detects them.

sample_rate

integerminimum: -9007199254740991maximum: 9007199254740991Sample rate in Hz. Required when audio_format is set.

language

stringLanguage code (e.g. "en", "fr", "de"). Used with format=true to enable Inverse Text Normalization. xAI transcribes in any language regardless — supplying this enables number/currency formatting in the transcript.

format

booleanWhen true, enables Inverse Text Normalization — spoken numbers and currencies are converted to written form (e.g. "one hundred dollars" → "$100"). Requires language to be set.

diarize

booleanWhen true, enables speaker diarization. Each word in the response includes a `speaker` integer identifying the detected speaker.

filler_words

booleanWhen true, filler words (uh, um, er) are included in the transcript. Defaults to false — filler words are removed.

multichannel

booleanWhen true, each audio channel is transcribed independently. Results are returned in the `channels` array. Requires channels ≥ 2.

channels

integerminimum: 2maximum: 8Number of audio channels (2–8). Required only for multichannel raw audio; auto-detected for container formats.

▶keyterm[]

arraymaxItems: 100Key terms to bias transcription toward (e.g. product names, proper nouns). Each term up to 50 characters, max 100 terms. Sent as repeated form fields: keyterm=Term+One&keyterm=Term+Two.

text

stringFull transcript text.

language

stringDetected language name (e.g. "English", "French").

duration

numberAudio duration in seconds (2 d.p.).

▶words[]

arrayWord-level segments. Each entry has text, start, end (seconds). Includes speaker integer when diarize=true.

▶channels[]

arrayPer-channel transcripts when multichannel=true.

API Schemas (Raw)

Input

Output