WebTransport: Low-Latency Bidirectional Streams over HTTP/3

WebSockets use a single ordered stream over TCP, causing head-of-line blocking for real-time applications like gaming or video that need multiple independent low-latency channels.

WebTransport is a browser API that uses HTTP/3 (QUIC) to provide multiple independent streams and datagrams with no head-of-line blocking.

// WebTransport client (Chrome 97+, browser only)
const transport = new WebTransport('https://example.com:4433/game');
await transport.ready;

// Unordered, unreliable datagrams (like UDP)
const writer = transport.datagrams.writable.getWriter();
await writer.write(new Uint8Array([1, 2, 3]));

// Ordered, reliable bidirectional streams
const stream = await transport.createBidirectionalStream();
const streamWriter = stream.writable.getWriter();
await streamWriter.write(encoder.encode('hello'));
const reader = stream.readable.getReader();
const { value } = await reader.read();

QUIC multiplexes streams at the UDP level — a dropped packet only stalls the one stream it belongs to, not all streams. This makes WebTransport ideal for games, video conferencing, and financial tickers where multiple independent data channels are needed.