Verify server supports TLS 1.3 and optional 0-RTT capability.
The TLS 1.3 Feature Checker confirms that a server supports TLS 1.3 and reports optional capabilities such as 0-RTT (early data). TLS 1.3 improves security and often latency; 0-RTT allows sending application data on the first flight when resuming a session. The tool performs a TLS 1.3 handshake and, where applicable, tests 0-RTT acceptance. Use it to validate that your host is offering TLS 1.3 and to see if 0-RTT is enabled—useful for performance tuning and for ensuring 0-RTT is only used where replay is acceptable.
Faster handshake, stronger ciphers, no legacy options; better security and often better performance.
Resumption feature that lets the client send data in the first round-trip; can have replay implications.
Use only for idempotent or replay-safe operations; servers may limit 0-RTT or reject it for sensitive actions.
In your server or load balancer config, enable TLS 1.3 and prefer it over 1.2; most modern stacks support it.
No. It only connects and observes handshake and optional 0-RTT; no configuration changes.