/Web APIs

WebTransport: datagrams property

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

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

The datagrams read-only property of the WebTransport interface returns a WebTransportDatagramDuplexStream instance that can be used to send and receive datagrams — unreliable data transmission.

"Unreliable" means that transmission of data is not guaranteed, nor is arrival in a specific order. This is fine in some situations and provides very fast delivery. For example, you might want to transmit regular game state updates where each message supersedes the last one that arrives, and order is not important.

Note: This feature is available in Web Workers



Writing an outgoing datagram

The WebTransportDatagramDuplexStream.writable property returns a WritableStream object that you can write data to using a writer, for transmission to the server:

const writer = transport.datagrams.writable.getWriter();
const data1 = new Uint8Array([65, 66, 67]);
const data2 = new Uint8Array([68, 69, 70]);

Reading an incoming datagram

The WebTransportDatagramDuplexStream.readable property returns a ReadableStream object that you can use to receive data from the server:

async function readData() {
  const reader = transport.datagrams.readable.getReader();
  while (true) {
    const { value, done } = await reader.read();
    if (done) {
    // value is a Uint8Array.


Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
datagrams 97 97 No No 83 No 97 97 No 68 No 18.0

See also

© 2005–2023 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.