WebTransportDatagramDuplexStream: maxDatagramSize property

Baseline 2026

Newly available

Since March 2026, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

Note: This feature is available in Web Workers.

The maxDatagramSize read-only property of the WebTransportDatagramDuplexStream interface returns the maximum allowable size of outgoing datagrams, in bytes, that can be written to writable.

Value

A number.

Examples

const url = "https://example.com:4999/wt";

async function initTransport(url) {
  // Initialize transport connection
  const transport = new WebTransport(url);

  // The connection can be used once ready fulfills
  await transport.ready;

  const datagrams = transport.datagrams;

  // get maxDatagramSize
  console.log(datagrams.maxDatagramSize);
}