Transcribe speech to text by using the API

This page shows you how to send a speech recognition request to Speech-to-Text using the REST interface and the curl command.

Speech-to-Text enables easy integration of Google speech recognition technologies into developer applications. You can send audio data to the Speech-to-Text API, which then returns a text transcription of that audio file. For more information about the service, see Speech-to-Text basics.

Before you begin

Before you can send a request to the Speech-to-Text API, you must have completed the following actions. See the before you begin page for details.

  • Enable Speech-to-Text on a GCP project.
    1. Make sure billing is enabled for Speech-to-Text.
  • Install the Google Cloud CLI, then initialize it by running the following command:

    gcloud init
  • (Optional) Create a new Google Cloud Storage bucket to store your audio data.

Make an audio transcription request

Now you can use Speech-to-Text to transcribe an audio file to text. Use the following code sample to send a recognize REST request to the Speech-to-Text API.

  1. Create a JSON request file with the following text, and save it as a sync-request.json plain text file:

      "config": {
          "sampleRateHertz": 16000,
          "languageCode": "en-US",
          "enableWordTimeOffsets": false
      "audio": {

    This JSON snippet indicates that the audio file has a FLAC encoding format, a sample rate of 16000 Hz, and that the audio file is stored on Google Cloud Storage at the given URI. The audio file is publicly accessible, so you don't need authentication credentials to access the file.

  2. Use curl to make a speech:recognize request, passing it the filename of the JSON request you set up in step 1:

    The sample curl command uses the gcloud auth print-access-token command to get an authentication token.

    curl -s -H "Content-Type: application/json" \
        -H "Authorization: Bearer "$(gcloud auth print-access-token) \ \
        -d @sync-request.json

    Note that to pass a filename to curl you use the -d option (for "data") and precede the filename with an @ sign. This file should be in the same directory in which you execute the curl command.

    You should see a response similar to the following:

      "results": [
          "alternatives": [
              "transcript": "how old is the Brooklyn Bridge",
              "confidence": 0.98267895

Congratulations! You've sent your first request to Speech-to-Text.

If you receive an error or an empty response from Speech-to-Text, take a look at the troubleshooting and error mitigation steps.

Clean up

To avoid incurring charges to your Google Cloud account for the resources used on this page, follow these steps.

What's next