SpeechRecognition: available() static method

Syntax

available(options)

Parameters

options

An object specifying options for the availability check. Possible properties include:

langs

An array of one or more strings containing BCP 47 language tags, each representing a language to check for availability. Passing an empty langs array will not throw an error, but the return value will always resolve to unavailable.

quality Optional

An enumerated value that indicates the approximate use case of your speech recognition app, and therefore, the required level of complexity of the language pack and speech recognition service. Possible values are:

command

Level 1: Short isolated phrases with limited vocabulary and a single speaker. Use cases include voice commands for apps. This is the default value.

dictation

Level 2: Continuous speech with moderate background noise and a single primary speaker. Use cases include dictating long-form text inputs such as SMS messages, email bodies, or strings for translation.

conversation

Level 3: Continuous speech with complex vocabulary, high background noise tolerance, and multiple primary speakers. Use cases include transcribing meetings and continuous live captioning.

processLocally Optional

A boolean that specifies whether to check availability of the languages only for on-device speech recognition (true) or for on-device or remote speech recognition (false). The default value is false.

Note: It is not possible to use available() to guarantee that a remote service supports the specified languages. A value of false means that either an on-device or a remote speech recognition service supports them.

Return value

A Promise that resolves with an enumerated value indicating the availability of the specified languages for speech recognition.

Possible values include:

available

Indicates that all the specified languages are supported at the given quality level.

• If processLocally is set to true, available means that speech recognition is available for those languages on-device (the required language packs have been downloaded and installed on the user's computer).
• If processLocally is set to false, available means that speech recognition is available for those languages either on-device or remotely.

downloading

Indicates that all the specified languages are supported at the given quality level for on-device processing, and that the relevant language pack for at least one language is in the process of being downloaded. Only relevant when processLocally is true.

downloadable

Indicates that support for the specified languages is available on-device, at the specified quality level, but the relevant language pack for at least one language has not yet been downloaded. Only relevant when processLocally is true.

unavailable

Indicates that at least one of the specified languages is not supported at the given quality level.

• If processLocally is set to true, unavailable means that on-device speech recognition is not available for at least one of the specified languages.
• If processLocally is set to false, unavailable means that speech recognition is not available for at least one of the specified languages either on-device or remotely.

Final return value for multiple languages with different statuses

Only one status value is returned, even if multiple languages are specified in the langs array. If different specified languages have different availability statuses, the final return value is the "furthest away" status from available for any of the languages, in the order shown in the following lists:

If processLocally is false:

• If all languages are available, then return available.
• Otherwise, return unavailable.

If processLocally is true:

• If all languages are available, return available.
• If at least one language is downloading, return downloading.
• If at least one language is downloadable, return downloadable.
• If at least one language is unavailable, return unavailable.

Exceptions

InvalidStateError DOMException

The current document is not fully active.

SyntaxError DOMException

One or more of the strings specified in langs is not a valid BCP 47 language tag.

Examples

Checking on-device availability and installing language packs

For on-device speech recognition to work, the browser must have a language pack installed for the language you want to recognize. If you run the start() method after specifying processLocally = true but the correct language pack isn't installed, the function call will fail with a language-not-supported error.

To get the correct language pack installed, ensure you follow these two steps:

1. Check whether the language pack is available on the user's computer using the available() method.
2. Install the language pack if it isn't available using the SpeechRecognition.install() method.

These steps are handled using the following code snippet:

startBtn.addEventListener("click", () => {
  // Check availability of target language
  SpeechRecognition.available({ langs: ["en-US"], processLocally: true }).then(
    (result) => {
      if (result === "unavailable") {
        diagnostic.textContent = `en-US not available to download at this time. Sorry!`;
      } else if (result === "available") {
        recognition.start();
        console.log("Ready to receive a color command.");
      } else {
        diagnostic.textContent = `en-US language pack downloading`;
        SpeechRecognition.install({
          langs: ["en-US"],
          processLocally: true,
        }).then((result) => {
          if (result) {
            diagnostic.textContent = `en-US language pack downloaded. Try again.`;
          } else {
            diagnostic.textContent = `en-US language pack failed to download. Try again later.`;
          }
        });
      }
    },
  );
});

We first run the available() method, specifying one language (langs: ["en-US"]) to check availability for, and processLocally: true. We test for three different possibilities of the return value:

• If the resulting value is unavailable, it means that no suitable language pack is available to download. We also print an appropriate message to the output.
• If the resulting value is available, it means that the language pack is available locally, so recognition can begin. In this case, we run start() and log a message to the console when the app is ready to receive speech.
• If the value is something else (downloadable or downloading), we print a diagnostic message to inform the user that a language pack download is starting, then run the install() method to handle the download.

The install() method starts the en-US language pack downloading and returns a Promise that resolves with a boolean indicating whether the specified language packs were downloaded and installed successfully (true) or not (false).

This code is excerpted from our on-device speech color changer (run the demo live). See Using the Web Speech API for a full explanation.

Checking on-device model capabilities

The following code snippet is a modification of the previous example in which we call the available() method with the quality option set to dictation, to check whether on-device recognition will support this quality level. If the result returned is unavailable, we set the SpeechRecognition object's processLocally property to false (assuming it was previously set to true) to force the API to use a cloud recognition service, then start() the recognition service.

If the result is available, we are good to go, so we just call start() to start on-device recognition. If the result is any other value, we run the install() method with the quality option set to dictation to install the required language packs.

startBtn.addEventListener("click", () => {
  // Check availability of on-device target language dictation quality
  SpeechRecognition.available({
    langs: ["en-US"],
    processLocally: true,
    quality: "dictation",
  }).then((result) => {
    if (result === "unavailable") {
      diagnostic.textContent = `On-device recognition for dictation not available, running with cloud recognition`;
      recognition.processLocally = false;
      recognition.start();
    } else if (result === "available") {
      recognition.start();
      console.log("Ready to receive a color command.");
    } else {
      diagnostic.textContent = `en-US language pack downloading`;
      SpeechRecognition.install({
        langs: ["en-US"],
        processLocally: true,
        quality: "dictation",
      }).then((result) => {
        if (result) {
          diagnostic.textContent = `en-US language pack downloaded. Try again.`;
        } else {
          diagnostic.textContent = `en-US language pack failed to download. Try again later.`;
        }
      });
    }
  });
});

Specifications

Browser compatibility

See also

• Web Speech API
• Using the Web Speech API
• SpeechRecognition.processLocally
• SpeechRecognition.install()