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 appendBufferAsync() method of the SourceBuffer interface 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 msBuffer.appendBufferAsync(buffer);
  } 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

BCD tables only load in the browser

See also