RTCDataChannel: bufferedAmountLowThreshold property

The RTCDataChannel property bufferedAmountLowThreshold is used to specify the number of bytes of buffered outgoing data that is considered "low." The default value is 0. When the number of buffered outgoing bytes, as indicated by the bufferedAmount property, falls to or below this value, a bufferedamountlow event is fired. This event may be used, for example, to implement code which queues more messages to be sent whenever there's room to buffer them. Listeners may be added with onbufferedamountlow or addEventListener().

The user agent may implement the process of actually sending data in any way it chooses; this may be done periodically during the event loop or truly asynchronously. As messages are actually sent, this value is reduced accordingly.

Note: bufferedamountlow events are not fired after the data channel is closed.


The number of queued outgoing data bytes below which the buffer is considered to be "low."


In this snippet of code, bufferedAmountLowThreshold is set to 64kB, and a handler for the bufferedamountlow event is established by setting the onbufferedamountlow property to a function which should send more data into the buffer by calling send().

const dc = peerConnection.createDataChannel("File Transfer");
dc.bufferedAmountLowThreshold = 65535;

dc.onbufferedamountlow = () => {
  /* use send() to queue more data to be sent */


WebRTC: Real-Time Communication in Browsers
# dom-rtcdatachannel-bufferedamountlowthreshold

Browser compatibility

BCD tables only load in the browser

See also