SpeechSynthesisUtterance: start event

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨September 2018⁩.

The start event of the Web Speech API SpeechSynthesisUtterance object is fired when the utterance has begun to be spoken.

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("start", (event) => { })

onstart = (event) => { }

In addition to the properties listed below, properties from the parent interface, Event, are available.

charIndex Read only: Returns the index position of the character in the SpeechSynthesisUtterance.text that was being spoken when the event was triggered.
elapsedTime Read only: Returns the elapsed time in seconds after the SpeechSynthesisUtterance.text started being spoken that the event was triggered at.
name Read only: Returns the name associated with certain types of events occurring as the SpeechSynthesisUtterance.text is being spoken: the name of the SSML marker reached in the case of a mark event, or the type of boundary reached in the case of a boundary event.
utterance Read only: Returns the SpeechSynthesisUtterance instance that the event was triggered on.

You can use the start event in an addEventListener method:

utterThis.addEventListener("start", (event) => {
  console.log(`We have started uttering this speech: ${event.utterance.text}`);
});

Or use the onstart event handler property:

utterThis.onstart = (event) => {
  console.log(`We have started uttering this speech: ${event.utterance.text}`);
};

Specification
Web Speech API # eventdef-speechsynthesisutterance-start
Web Speech API # dom-speechsynthesisutterance-onstart

This page was last modified on ⁨May 2, 2025⁩ by MDN contributors.