RTCSctpTransport: maxMessageSize property

The maxMessageSize read-only property of the RTCSctpTransport interface indicates the maximum size of a message that can be sent using the RTCDataChannel.send() method.


An integer value giving the maximum size, in bytes, of a message which can be sent using the RTCDataChannel.send() method.


This example shows how you might split up a string into small enough parts to send based on maximum message size.

// Function splits strings to a specified size and returns array.
function splitStringToMax(str, maxLength) {
  const result = [];
  let i = 0;
  while (i < str.length) {
    result.push(str.substring(i, i + maxLength));
    i += maxLength;
  return result;

const peerConnection = new RTCPeerConnection(options);
const channel = peerConnection.createDataChannel("chat");
channel.onopen = (event) => {
  const maximumMessageSize = peerConnection.sctp.maxMessageSize;
  const textToSend = "This is my possibly overly long string!";
  splitStringToMax(textToSend, maximumMessageSize).forEach((elem) => {


WebRTC: Real-Time Communication in Browsers
# dom-rtcsctptransport-maxmessagesize

Browser compatibility

BCD tables only load in the browser

See also