RTCDataChannel: bufferedamountlow event

A bufferedamountlow event is sent to an RTCDataChannel when the number of bytes currently in the outbound data transfer buffer falls below the threshold specified in bufferedAmountLowThreshold. bufferedamountlow events aren't sent if bufferedAmountLowThreshold is 0.

This event is not cancelable and does not bubble.


Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("bufferedamountlow", (event) => {});

onbufferedamountlow = (event) => {};

Event type

A generic Event.


This example sets up a handler for bufferedamountlow to request more data any time the data channel's buffer falls below the number of bytes specified by bufferedAmountLowThreshold, which we have set to 65536. In other words, we'll try to keep at least 64kB of data in the buffer, reading 64kB at a time from the source.

let pc = new RTCPeerConnection();
let dc = pc.createDataChannel("SendFile");
// source data object
let source = (dc.bufferedAmountLowThreshold = 65536);

  (ev) => {
    if (source.position <= source.length) {

After creating the RTCPeerConnection, this calls RTCPeerConnection.createDataChannel() to create the data channel. Then a listener is created for bufferedamountlow to refill the incoming data buffer any time its contents fall below 65536 bytes.

You can also set up a listener for bufferedamountlow using its event handler property, onbufferedamountlow:

pc.onbufferedamountlow = (ev) => {
  if (source.position <= source.length) {


WebRTC: Real-Time Communication in Browsers
# event-datachannel-bufferedamountlow
WebRTC: Real-Time Communication in Browsers
# dom-rtcdatachannel-onbufferedamountlow

Browser compatibility

BCD tables only load in the browser

See also