This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The default property of the HTMLTrackElement interface represents whether the track will be enabled if the user's preferences do not indicate that another track would be more appropriate. It reflects the <track> element's boolean default attribute, returning true if present and false otherwise.
A Boolean.
const trackElement = document.getElementById("exampleTrack");
console.log(trackElement.default);
trackElement.default = true;
| Specification |
|---|
| HTML> # dom-track-default> |
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Opera | Safari | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | WebView Android | WebView on iOS | |
default |
23 | 12 | 31 | 12 | 6 | 25 | 31 | 12 | 6 | 1.5 | 4.4 | 6 |
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https://developer.mozilla.org/en-US/docs/Web/API/HTMLTrackElement/default