xai/speech-to-text/v1

xAI's Grok Speech-to-Text — fast, accurate transcription across 25 languages with speaker diarization, word-level timestamps, multichannel audio, and inverse text normalization.

Inference

Commercial use

Streaming

Partner

Schema

LLMs

Playground API

About

Transcribe audio using xAI's Speech-to-Text API.

Supports 25 languages with optional speaker diarization, Inverse Text Normalization (punctuation & formatting), and per-channel transcription for multi-channel audio. Returns word-level timestamps.

1. Calling the API#

Install the client#

The client provides a convenient way to interact with the model API.

npm install --save @fal-ai/client

Migrate to @fal-ai/client

The @fal-ai/serverless-client package has been deprecated in favor of @fal-ai/client. Please check the migration guide for more information.

Setup your API Key#

Set FAL_KEY as an environment variable in your runtime.

export FAL_KEY="YOUR_API_KEY"

Submit a request#

The client API handles the API submit protocol. It will handle the request status updates and return the result when the request is completed.

import { fal } from "@fal-ai/client";

const result = await fal.subscribe("xai/speech-to-text/v1", {
  input: {
    audio_url: "https://storage.googleapis.com/falserverless/model_tests/whisper/dinner_conversation.mp3"
  },
  logs: true,
  onQueueUpdate: (update) => {
    if (update.status === "IN_PROGRESS") {
      update.logs.map((log) => log.message).forEach(console.log);
    }
  },
});
console.log(result.data);
console.log(result.requestId);

Streaming#

This model supports streaming requests. You can stream data directly to the model and get the result in real-time.

import { fal } from "@fal-ai/client";

const stream = await fal.stream("xai/speech-to-text/v1", {
  input: {
    audio_url: "https://storage.googleapis.com/falserverless/model_tests/whisper/dinner_conversation.mp3"
  }
});

for await (const event of stream) {
  console.log(event);
}

const result = await stream.done();

2. Authentication#

The API uses an API Key for authentication. It is recommended you set the FAL_KEY environment variable in your runtime when possible.

API Key#

In case your app is running in an environment where you cannot set environment variables, you can set the API Key manually as a client configuration.

import { fal } from "@fal-ai/client";

fal.config({
  credentials: "YOUR_FAL_KEY"
});

Protect your API Key

When running code on the client-side (e.g. in a browser, mobile app or GUI applications), make sure to not expose your FAL_KEY. Instead, use a server-side proxy to make requests to the API. For more information, check out our server-side integration guide.

3. Queue#

Long-running requests

For long-running requests, such as training jobs or models with slower inference times, it is recommended to check the Queue status and rely on Webhooks instead of blocking while waiting for the result.

Submit a request#

The client API provides a convenient way to submit requests to the model.

import { fal } from "@fal-ai/client";

const { request_id } = await fal.queue.submit("xai/speech-to-text/v1", {
  input: {
    audio_url: "https://storage.googleapis.com/falserverless/model_tests/whisper/dinner_conversation.mp3"
  },
  webhookUrl: "https://optional.webhook.url/for/results",
});

Fetch request status#

You can fetch the status of a request to check if it is completed or still in progress.

import { fal } from "@fal-ai/client";

const status = await fal.queue.status("xai/speech-to-text/v1", {
  requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b",
  logs: true,
});

Get the result#

Once the request is completed, you can fetch the result. See the Output Schema for the expected result format.

import { fal } from "@fal-ai/client";

const result = await fal.queue.result("xai/speech-to-text/v1", {
  requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b"
});
console.log(result.data);
console.log(result.requestId);

4. Files#

Some attributes in the API accept file URLs as input. Whenever that's the case you can pass your own URL or a Base64 data URI.

Data URI (base64)#

You can pass a Base64 data URI as a file input. The API will handle the file decoding for you. Keep in mind that for large files, this alternative although convenient can impact the request performance.

Hosted files (URL)#

You can also pass your own URLs as long as they are publicly accessible. Be aware that some hosts might block cross-site requests, rate-limit, or consider the request as a bot.

Uploading files#

We provide a convenient file storage that allows you to upload files and use them in your requests. You can upload files using the client API and use the returned URL in your requests.

import { fal } from "@fal-ai/client";

const file = new File(["Hello, World!"], "hello.txt", { type: "text/plain" });
const url = await fal.storage.upload(file);

Auto uploads

The client will auto-upload the file for you if you pass a binary object (e.g. File, Data).

Read more about file handling in our file upload guide.

5. Schema#

Input#

audio_url string* required

URL of the audio file to transcribe. Supported formats: mp3, wav, ogg, opus, flac, aac, mp4, m4a, mkv.

language LanguageEnum

BCP-47 language code for the audio, or 'auto' to let xAI detect the language automatically. Supported: ar, cs, da, de, en, es, fa, fil, fr, hi, id, it, ja, ko, mk, ms, nl, pl, pt, ro, ru, sv, th, tr, vi. Default value: "auto"

Possible enum values: auto, ar, cs, da, de, en, es, fa, fil, fr, hi, id, it, ja, ko, mk, ms, nl, pl, pt, ro, ru, sv, th, tr, vi

diarize boolean

Whether to enable speaker diarization. When enabled, each word in the response includes a speaker integer indicating the detected speaker.

format boolean

Whether to apply Inverse Text Normalization (ITN) to the transcript — adds punctuation, capitalization, and formats numbers/digits. Set to false to get unformatted output. Note: xAI requires a specific language for ITN, so this flag is automatically disabled when language='auto'. Default value: true

multichannel boolean

Whether to transcribe each audio channel independently. When enabled, per-channel transcripts are returned in the channels array.

{
  "audio_url": "https://storage.googleapis.com/falserverless/model_tests/whisper/dinner_conversation.mp3",
  "language": "auto",
  "format": true
}

Output#

text string* required

The full transcribed text.

language string* required

BCP-47 language code detected (or echoed) by xAI.

duration float

Duration of the audio in seconds as reported by xAI.

words list<TranscriptionWord>

Word-level transcription with timestamps.

channels list<TranscriptionChannel>

Per-channel transcripts. Only populated when multichannel=true was requested.

{
  "text": "The future belongs to those who believe in the beauty of their dreams.",
  "language": "en",
  "duration": 12.34,
  "words": [
    {
      "text": ""
    }
  ],
  "channels": [
    {
      "text": "",
      "words": [
        {
          "text": ""
        }
      ]
    }
  ]
}

Other types#

TranscriptionChannel#

index integer* required

Zero-based channel index.

text string* required

Full transcript for this channel.

words list<TranscriptionWord>

Word-level breakdown for this channel.

TranscriptionWord#

speaker integer

Speaker index (0-based) when diarize=true was requested, otherwise null.

text string* required

The transcribed word or token.

start float

Start time of the word in seconds.

end float

End time of the word in seconds.

xai/speech-to-text/v1

Table of contents

1. Calling the API

2. Authentication

3. Queue

4. Files

5. Schema

About

1. Calling the API#

Install the client#

Migrate to @fal-ai/client

Setup your API Key#

Submit a request#

Streaming#

2. Authentication#

API Key#

Protect your API Key

3. Queue#

Long-running requests

Submit a request#

Fetch request status#

Get the result#

4. Files#

Data URI (base64)#

Hosted files (URL)#

Uploading files#

Auto uploads

5. Schema#

Input#

Output#

Other types#

TranscriptionChannel#

TranscriptionWord#