TLS session resumption allows clients and servers to reuse previously negotiated cryptographic parameters, significantly reducing the latency of subsequent TLS handshakes. There are two main mechanisms: session IDs (server-side cache) and session tickets (client-side encrypted tickets). Our tool tests both methods and reports whether your server supports them, along with performance measurements.
How to Use
Enter the domain name of the server you want to test.
Click "Check" to run the session resumption analysis.
Review the results showing session ID support, session ticket support, and handshake timing data.
Use the findings to optimize your TLS configuration for better performance.
Use Cases
•Verify that session resumption is properly configured on production servers
•Measure the performance benefit of enabling session tickets in high-traffic environments
•Troubleshoot slow TLS handshakes caused by missing session cache support
•Ensure load-balanced servers use consistent session cache configurations
Frequently Asked Questions
TLS session resumption lets a client and server reuse previously established cryptographic parameters, skipping the expensive public-key operations in a full TLS handshake. This reduces latency from two round trips to just one (or zero with 0-RTT).
Session IDs are stored on the server side, requiring the server to maintain a cache. Session tickets (RFC 5077) are encrypted and stored on the client, eliminating the server-side cache requirement and making them ideal for load-balanced environments.
Without session resumption, every new connection requires a full TLS handshake involving CPU-intensive asymmetric cryptography. With resumption, subsequent connections can be established in as little as one round trip, reducing page load times and server CPU usage significantly for sites with many returning visitors.
More than any other TLS optimisation, for the traffic that actually matters. A resumed handshake in TLS 1.3 removes most of the round trips a full one needs, and since most real sessions are repeat visits that is most of your connections. Unlike 0-RTT it carries no replay risk, which is why it should be enabled and 0-RTT is optional — the same saving, without the security caveat.
Because TLS 1.3 delivers tickets after the handshake completes, and this interface does not surface them, so the client-side cache never records a hit. The page therefore reports what it observed — a session was offered, and a reused-session connection completed — and states that this is not confirmation. Confirming it properly means measuring the handshake itself with timing tools, not inferring it from a completed connection.
That depends on the protocol version. Session identifiers belong to TLS 1.2 and earlier; TLS 1.3 replaced them with tickets, which carry the same purpose with better properties. The page names whichever the server issued, so a 1.2 deployment and a 1.3 deployment reporting different methods is expected rather than inconsistent.
Usually the version, not the configuration. On TLS 1.3 the ticket is delivered after the handshake in a message this client library does not expose, so the cache stays empty and the page cannot confirm. If you are on TLS 1.2 and still see nothing, the likelier causes are a short session cache lifetime or a server configured not to issue tickets for that context.
By timing repeated connections to the same host. A resumed TLS 1.3 handshake is roughly one round trip against two for a full one, which shows as a consistent drop in handshake time once the session cache is warm. Use a tool that reports per-phase handshake timings rather than total page load, and make enough repeat connections for the cache to fill before drawing conclusions.
What the Check Does
Resumption is only provable by resuming, so this page opens two connections: the first obtains a session, the second offers that session back and reports what happened.
1Connect once and keep the session the server offers, recording whether it arrived as a session identifier or a ticket. No session at all is reported plainly as no resumption mechanism.
2Connect a second time offering that session, and check whether the client's session cache records a hit. That cache hit is the only positive confirmation available here, and it is what the verdict is based on.
3Distinguish offered from honoured. A completed second connection is not proof: a full handshake would also succeed. Where no cache hit is recorded the result says so and does not claim resumption, because TLS 1.3 tickets are not exposed to this interface.
This page previously crashed on every host — the session identifier attribute was wrong and the result class was missing its dataclass decorator, so no result could be returned at all. It now reports observations with their limits attached.
Tips & Best Practices
•Enable session resumption to improve TLS handshake performance
•Monitor session resumption rates for performance optimization
•Configure appropriate session cache size for your traffic volume
•Balance session resumption benefits with security requirements
Technical Details
Mechanism: TLS session resumption (session IDs and session tickets) Performance: Handshake time reduction through session reuse Cache: Session cache configuration and management Output: Session resumption status with performance analysis
