This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

The trackDefaults property of the SourceBuffer interface specifies the default values to use if kind, label, and/or language information is not available in the initialization segment of the media to be appended to the SourceBuffer.


var myTrackDefaults = sourceBuffer.trackDefaults;

sourceBuffer.trackDefaults = myTrackDefaultList;


A TrackDefaultList object.


The following exceptions may be thrown when setting a new value for this property.

Exception Explanation
InvalidStateError One or more of the SourceBuffer objects in MediaSource.sourceBuffers are being updated (i.e. their SourceBuffer.updating property is currently true), or this SourceBuffer has been removed from the MediaSource.



Browser compatibility

BCD tables only load in the browser

See also