Speech synthesis

The Speech synthesis object can automatically speak some text using a synthetic voice, also known as text-to-speech (TTS).

Speech synthesis may not be supported by all browsers or platforms. Use the Supports speech synthesis condition to check if speech synthesis can be used.


This object has no script interface, because when using JavaScript or TypeScript coding you can use the browser built-in Web Speech API.

Speech synthesis conditions

Is speaking
True if the speech synthesis engine is currently reading out some text.
On speech ended
Triggered when the speech started by Speak text finishes being read out.
On speech error
Triggered if an error occurs during speech synthesis.
Supports speech synthesis
True if the current browser/platform supports speech synthesis, so the Speak text action can be used

Speech synthesis actions

Pause speaking
Resume speaking
Pause or resume text being read out by speech synthesis from the Speak text action.
Speak text
Read out some text using speech synthesis. The language, volume, rate and pitch of the voice that reads out the text can be customised. The Voice URI can be used to select a different kind of voice (e.g. male vs. female) from a list of the supported voices, if any alternatives are available. The list of possible voices can be retrieved using the VoiceCount and VoiceURIAt expressions.
Stop speaking
Stop reading out text from a previous Speak text action. The speech cannot be resumed.

Speech synthesis expressions

Return the number of voices available for use with speech synthesis.
Return the language, name, or URI of the voice at the given zero-based index. This can be used to show the user a list of possible voices to choose. To select a different voice, pass the appropriate voice URI to the Speak text action.
Construct 3 Manual 2024-02-16