> 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/the-protocol/feature-trans-app.md).

# Transport and application

The IETF QUIC protocol is a transport protocol, on top of which other application protocols can be used. The initial application layer protocol is HTTP/3 (h3).

The transport layer supports connections and streams.

The legacy Google version of QUIC had transport and HTTP glued together into one single do-it-all and was a more special-purpose send-http/2-frames-over-udp protocol.