MediaSource: activeSourceBuffers property

The activeSourceBuffers read-only property of the MediaSource interface returns a SourceBufferList object containing a subset of the SourceBuffer objects contained within sourceBuffers — the list of objects providing the selected video track, enabled audio tracks, and shown/hidden text tracks.


A SourceBufferList containing the SourceBuffer objects for each of the active tracks.


The following snippet is based on a simple example written by Nick Desaulniers (view the full demo live, or download the source for further investigation). The function getMediaSource(), which is not defined here, returns a MediaSource.

const mediaSource = getMediaSource();

function sourceOpen() {
  console.log(mediaSource.readyState); // open
  const sourceBuffer = mediaSource.addSourceBuffer(mimeCodec);
  fetchAB(assetURL, (buf) => {
    sourceBuffer.addEventListener("updateend", () => {
      // will contain the source buffer that was added above,
      // as it is selected for playing in the video player;
      console.log(mediaSource.readyState); // ended

// …


Media Source Extensions™
# dom-mediasource-activesourcebuffers

Browser compatibility

BCD tables only load in the browser

See also