This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

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

The SourceBuffer method appendBufferAsync() begins the process of asynchronously appending media segment data from an ArrayBuffer or ArrayBufferView object to the SourceBuffer. It returns a Promise which is fulfilled once the buffer has been appended.


appendPromise = sourceBuffer.appendBufferAsync(source);


A BufferSource (that is, either an ArrayBufferView or ArrayBuffer) which contains the media segment data you want to add to the SourceBuffer.

Return value

A Promise which is fulfilled when the buffer has been added successfully to the SourceBuffer, or null if the request could not be initiated.


This simplified example async function, fillSourceBuffer(), takes as input parameters BufferSource, buffer, and a SourceBuffer to which to append the source media from the buffer.

async function fillSourceBuffer(buffer, msBuffer) {
  try {
    while(true) {
      await buffer.appendBufferAsync(msBuffer);
  } catch(e) {


Not currently part of any specification. This is being experimented with under the auspices of the Web Platform Incubator Community Group (WICG).

Specification Status Comment
Media Source Extensions Recommendation Initial definition; does not include this method.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support No No621 No No No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support No Yes No621 No No ?

1. From version 62: this feature is behind the media.mediasource.experimental.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.

See also

Document Tags and Contributors

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