RTCDataChannel.bufferedAmount

The read-only RTCDataChannel property bufferedAmount returns the number of bytes of data currently queued to be sent over the data channel. The queue may build up as a result of calls to the send() method. This only includes data buffered by the user agent itself; it doesn't include any framing overhead or buffering done by the operating system or network hardware.

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.

Whenever this value decreases to fall to or below the value specified in the bufferedAmountLowThreshold property, the user agent fires the bufferedamountlow event. This event may be used, for example, to implement code which queues more messages to be sent whenever there's room to buffer them.

Syntax

var amount = aDataChannel.bufferedAmount;

Value

The number of bytes of data currently queued to be sent over the data channel but have not yet been sent.

Example

The snippet below includes a function which changes the contents of a block with the ID "bufferSize" to a string indicating the number of bytes currently buffered on an RTCDataChannel.

var dc = peerConnection.createDataChannel("File Transfer");

/* ... */

function showBufferedAmount(channel) {
  let el = document.getElementbyId("bufferSize");

  el.innerHTML = channel.bufferedAmount + " bytes";
}

Specifications

Specification	Status	Comment
WebRTC 1.0: Real-time Communication Between Browsers The definition of 'RTCDataChannel.bufferedAmount' in that specification.	Working Draft	Initial specification.

Browser compatibility

[1] The interface is called DataChannel and not RTCDataChannel in Firefox; however, a binding was added in Firefox 24 so that either name may be used.

See also

• WebRTC
• Using WebRTC data channels
• RTCDataChannel
• RTCDataChannel.bufferedAmountLowThreshold
• bufferedamountlow event
• RTCDataChannel.onbufferedamountlow