0-RTT (Zero Round Trip Time)
Embed This Widget
Add the script tag and a data attribute to embed this widget.
Embed via iframe for maximum compatibility.
<iframe src="proxy.php?url=https%3A%2F%2Fstatuscodefyi.com%2Fiframe%2Fglossary%2Fzero-rtt%2F" width="420" height="400" frameborder="0" style="border:0;border-radius:10px;max-width:100%" loading="lazy"></iframe>Paste this URL in WordPress, Medium, or any oEmbed-compatible platform.
https://statuscodefyi.com/glossary/zero-rtt/Add a dynamic SVG badge to your README or docs.
[](https://statuscodefyi.com/glossary/zero-rtt/)Use the native HTML custom element.
A TLS 1.3 feature (RFC 8446 Section 2.3) that allows a client to send application data in the very first message of a resumed session, before receiving any response from the server. This cuts perceived connection latency to near zero for returning visitors. The trade-off is that 0-RTT data is vulnerable to replay attacks — an attacker could retransmit the same 0-RTT data to trigger duplicate side effects. As a result, 0-RTT should only be used for idempotent, replay-safe requests such as HTTP GET or read-only API calls, and never for state-changing operations.