This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for the proper prefixes to use in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the spec changes.

The addSourceBuffer() method of the MediaSource interface creates a new SourceBuffer of the given MIME type and adds it to the MediaSource's SourceBuffers list.


var sourceBuffer = mediaSource.addSourceBuffer(mimeType);


The MIME type of the source buffer you want to create.


A SourceBuffer object.


The following errors may be thrown when calling this method.

Error Explanation
InvalidAccessError The supplied mimeType is an empty string.
InvalidStateError MediaSource.readyState is not equal to open.
NotSupportedError The supplied mimeType is not supported by the current browser, or it is not compatible with the mimeTypes specified for the SourceBuffer objects that already exist in MediaSource.sourceBuffers.
QuotaExceededError The user agent can't handle any more SourceBuffer objects, or creating a SourceBuffer based on this mimeType would result in an unsupported SourceBuffer configuration.


The following snippet is from a simple example written by Nick Desaulniers (view the full demo live, or download the source for further investigation.)

var assetURL = 'frag_bunny.mp4';
// Need to be specific for Blink regarding codecs
// ./mp4info frag_bunny.mp4 | grep Codec
var mimeCodec = 'video/mp4; codecs="avc1.42E01E, mp4a.40.2"';

if ('MediaSource' in window && MediaSource.isTypeSupported(mimeCodec)) {
  var mediaSource = new MediaSource;
  //console.log(mediaSource.readyState); // closed
  video.src = URL.createObjectURL(mediaSource);
  mediaSource.addEventListener('sourceopen', sourceOpen);
} else {
  console.error('Unsupported MIME type or codec: ', mimeCodec);

function sourceOpen (_) {
  //console.log(this.readyState); // open
  var mediaSource = this;
  var sourceBuffer = mediaSource.addSourceBuffer(mimeCodec);
  fetchAB(assetURL, function (buf) {
    sourceBuffer.addEventListener('updateend', function (_) {
      //console.log(mediaSource.readyState); // ended


Specification Status Comment
Media Source Extensions
The definition of 'addSourceBuffer()' in that specification.
Candidate Recommendation Initial definition.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 23 25.0 (25.0)[1]
42.0 (42.0)
11[2] 15 8
Feature Android Firefox Mobile (Gecko) Firefox OS (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support 4.4.4

Not supported

Not supported 11 30 Not supported

[1] Available after switching the about:config preference media.mediasource.enabled to true. In addition, support was limited to a whitelist of sites, for example YouTube, Netflix, and other popular streaming sites. The whitelist was removed and Media Source Extensions was enabled by default in 42+ for all sites.

[2] Only works on Windows 8+.

See also

Document Tags and Contributors

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