> 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/ja/the-protocol/feature-http.md).

# HTTP/3 over QUIC

HTTP/3 と呼ばれる HTTP レイヤーは HTTP に準拠したトランスポートを行います。HTTP ヘッダ圧縮では QPACK を利用しており、これは HTTP/2 における HPACK に似ています。

HPACK アルゴリズムはストリームが順番に届くことを前提としているため、修正せずに HTTP/3 で再利用することは不可能です。

これは QUIC の提供するストリームにおいては転送がばらばらに行われるためです。

QPACK は [HPACK](https://httpwg.org/specs/rfc7541.html) の QUIC 対応版といえます。


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