RTCSctpTransport: maxMessageSize property

Baseline 2023

Newly available

Since May 2023, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

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