WebTransport

WebTransport is a web platform API and protocol designed to enable low-latency client–server communication by leveraging QUIC and HTTP/3. It provides a session-based transport over a single connection that can carry multiple logical data channels between a client and a server, reducing the overhead of repeatedly establishing new connections. WebTransport exposes different data paths, including reliable, ordered bidirectional streams for stream-oriented data and datagrams for message-based communication. It also supports unidirectional streams to send data in one direction. The traffic on a WebTransport session is multiplexed, allowing many streams and datagrams to coexist efficiently.

WebTransport sessions begin with an HTTP/3 handshake that establishes a QUIC connection and negotiates a WebTransport session on top of it. After the session is established, the client and server can open and manage multiple streams and datagrams as needed. The WebTransport API exposes interfaces to create and manage these streams and datagrams, monitor readiness, and handle incoming data and closures, enabling fine-grained control over data flow and timing.

Use cases for WebTransport include real-time multiplayer gaming, live collaboration tools, streaming telemetry, and other latency-sensitive applications where WebSockets may be limited or less flexible. Compared with WebSockets, WebTransport offers multiplexed streams and datagrams with selectable reliability and ordering semantics, aiming to provide lower latency and more efficient data transport. The technology is under ongoing standardization by WHATWG and the W3C, with implementations in some Chromium-based browsers and evolving server support to handle HTTP/3 and QUIC-based sessions.

Security and privacy are built on the underlying TLS 1.3 and QUIC security model, with the same-origin policy and web platform security principles applying to WebTransport connections.