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This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

This page is not complete.

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 errors may be thrown when setting a new value for this property.

Error 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.




Specification Status Comment
Media Source Extensions
The definition of 'trackDefaults' in that specification.
Recommendation Initial definition.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support ? ? No ? ? ?
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support ? ? ? No ? No ?

See also

Document Tags and Contributors

 Contributors to this page: fscholz, chrisdavidmills
 Last updated by: fscholz,