> 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/quic/quic-0rtt.md).

# 0-RTT

To reduce the time required to establish a new connection, a client that has previously connected to a server may cache certain parameters from that connection and subsequently set up a **0-RTT** connection with the server. This allows the client to send data immediately, without waiting for a handshake to complete.