> 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-h2.md).

# Comparison with HTTP/2

HTTP/3 is designed for QUIC, which is a transport protocol that handles streams by itself.

HTTP/2 is designed for TCP, and therefore handles streams in the HTTP layer.

## Similarities

The two protocols offer clients virtually identical feature sets.

* Both protocols offer server push support
* Both protocols have header compression, and QPACK and HPACK are similar in design.
* Both protocols offer multiplexing over a single connection using streams

## Differences

The differences are in the details and primarily there thanks to HTTP/3's use of QUIC:

* HTTP/3 has better and more likely to work early data support thanks to QUIC's 0-RTT handshakes, while TCP Fast Open and TLS usually sends less data and often faces problems.
* HTTP/3 has much faster handshakes thanks to QUIC vs TCP + TLS.
* HTTP/3 does not exist in an insecure or unencrypted version. HTTP/2 can be implemented and used without HTTPS - even if this is rare on the Internet.
* HTTP/2 can be negotiated directly in a TLS handshake with the ALPN extension, while HTTP/3 is over QUIC so it needs an `Alt-Svc:` header response first to inform the client about this fact.
* The base HTTP/3 specification doesn't define prioritization itself. The HTTP/2 approach to prioritization has been deemed too complicated and is deprecated by the latest revision of the HTTP/2 specification [RFC 9113](https://www.rfc-editor.org/rfc/rfc9113.html). A simpler alternative, the Extensible Prioritization Scheme for HTTP ([RFC 9218](https://www.rfc-editor.org/rfc/rfc9218.html)), has been published separately, which can be used in both HTTP/2 and HTTP/3.