WebTransportDatagramDuplexStream: outgoingHighWaterMark 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 outgoingHighWaterMark property of the WebTransportDatagramDuplexStream interface gets or sets the high water mark for outgoing chunks of data — this is the maximum size, in chunks, that the outgoing WritableStream's internal queue can reach before it is considered full. See Internal queues and queuing strategies for more information.

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;

  // set outgoingHighWaterMark
  datagrams.outgoingHighWaterMark = 20000;

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