WebTransport: incomingUnidirectionalStreams 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 incomingUnidirectionalStreams read-only property of the WebTransport interface represents one or more unidirectional streams opened by the server. Returns a ReadableStream of WebTransportReceiveStream objects. Each one can be used to reliably read data from the server.
"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.
Value
A ReadableStream of WebTransportReceiveStream objects.
Examples
An initial function is used to read the WebTransportReceiveStream objects from the ReadableStream. Each object is then passed to another function to read from those streams.
async function receiveUnidirectional() {
const uds = transport.incomingUnidirectionalStreams;
const reader = uds.getReader();
while (true) {
const { done, value } = await reader.read();
if (done) {
break;
}
// value is an instance of WebTransportReceiveStream
await readData(value);
}
}
async function readData(receiveStream) {
const reader = receiveStream.getReader();
while (true) {
const { done, value } = await reader.read();
if (done) {
break;
}
// value is a Uint8Array
console.log(value);
}
}
Specifications
| Specification |
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| WebTransport # dom-webtransport-incomingunidirectionalstreams |
Browser compatibility
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incomingUnidirectionalStreams
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Legend
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- User must explicitly enable this feature.