Use fetch --webtransport https://host/path to open a WebTransport session.
WebTransport uses HTTP/3 over a direct UDP connection. It does not support
proxies, Unix sockets, redirects, retries, output files, formatting, or
Digest authentication.
The default mode is one reliable bidirectional stream. -d and -j are sent
after the session handshake, followed by piped standard input. The stream is
closed for writing at EOF, but fetch continues to read until the peer closes.
Stream output is raw bytes when stdout is redirected and is escaped when it is
a terminal.
Use --wt-mode datagram for unreliable datagrams. --wt-datagram-mode lines
sends one datagram per line; binary sends 1 KiB chunks. Received datagrams
are JSON Lines records with sequence, length, and base64 data fields.
If an outgoing datagram is too large, the error reports its size and the
current underlying QUIC limit (before HTTP/3 framing overhead).
Datagram input ending does not close the session. Use Ctrl+C when the peer does
not close it.
Repeat --wt-protocol to advertise application protocols. Protocols are
validated and sent in offer order. --dry-run prints the CONNECT metadata and
does not resolve DNS, open UDP, or consume standard input.
This implementation uses WebTransport draft-16. Use HTTPS and TLS 1.3-capable HTTP/3 servers.