> For the complete documentation index, see [llms.txt](https://http3-explained.haxx.se/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://http3-explained.haxx.se/en/h3/h3-streams.md).

# QUIC streams and HTTP/3

HTTP/3 is made for QUIC so it takes full advantage of QUIC's streams, where HTTP/2 had to design its entire stream and multiplexing concept of its own on top of TCP.

HTTP requests done over HTTP/3 use a specific set of streams.

## HTTP/3 frames

HTTP/3 means setting up QUIC streams and sending over a set of frames to the other end. There's but a small fixed number (actually nine on December 18th, 2018!) of known frames in HTTP/3. The most important ones are probably:

* HEADERS, that sends compressed HTTP headers
* DATA, sends binary data contents
* GOAWAY, please shutdown this connection

## HTTP Request

The client sends its HTTP request on a client-initiated *bidirectional* QUIC stream.

A request consists of a single HEADERS frame and might optionally be followed by one or two other frames: a series of DATA frames and possibly a final HEADERS frame for trailers.

After sending a request, a client closes the stream for sending.

## HTTP Response

The server sends back its HTTP response on the bidirectional stream. A HEADERS frame, a series of DATA frames and possibly a trailing HEADERS frame.

## QPACK headers

The HEADERS frames contain HTTP headers compressed using the QPACK algorithm. QPACK is similar in style to the HTTP/2 compression called HPACK ([RFC 7541](https://httpwg.org/specs/rfc7541.html)), but modified to work with streams delivered out of order.

QPACK itself uses two additional unidirectional QUIC streams between the two end-points. They are used to carry dynamic table information in either direction.


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