/Web APIs

WebTransport: incomingBidirectionalStreams 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 incomingBidirectionalStreams read-only property of the WebTransport interface represents one or more bidirectional streams opened by the server. Returns a ReadableStream of WebTransportBidirectionalStream objects. Each one can be used to reliably read data from the server and write data back to it.

"Reliable" means that transmission and order of data are guaranteed. This provides slower delivery (albeit faster than with WebSockets) than datagrams, but is needed in situations where reliability and ordering are important, like chat applications.

Note: This feature is available in Web Workers



An initial function is used to read the WebTransportBidirectionalStream objects from the ReadableStream. For each one, the WebTransportBidirectionalStream.readable and WebTransportBidirectionalStream.writable values are passed to other functions to read from and write to those streams.

async function receiveBidirectional() {
  const bds = transport.incomingBidirectionalStreams;
  const reader = bds.getReader();
  while (true) {
    const { done, value } = await reader.read();
    if (done) {
    // value is an instance of WebTransportBidirectionalStream
    await readData(value.readable);
    await writeData(value.writable);

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

async function writeData(writable) {
  const writer = writable.getWriter();
  const data1 = new Uint8Array([65, 66, 67]);
  const data2 = new Uint8Array([68, 69, 70]);


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
incomingBidirectionalStreams 97 97 No No 83 No 97 97 No 68 No 18.0

See also

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