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OmnvertImage • Document • Network

TLS/SSL Checker

Check TLS version, ALPN, cipher, certificate chain, SANs, and expiry of any host.

Server-sideProcessed server-side

This tool uses a server-side service for processing; uploaded files or requests are not kept for long-term storage.

About

This TLS checker helps you validate HTTPS configuration for a domain. It’s useful when you see certificate warnings, handshake errors, or need to confirm what protocol/cipher the server negotiates.

You can inspect certificate chain details, subject alternative names (SANs), and expiry dates to plan renewals and avoid downtime. ALPN information can also help confirm HTTP/2 or HTTP/3 negotiation paths depending on server support.

If results look different from your browser, remember that CDNs, geo routing, and SNI/ALPN negotiation can vary. Always test the exact hostname users visit, including www vs non-www.

How it works

  1. 1Open TLS/SSL Checker and choose your file or enter the required input.
  2. 2Check the settings and start the process.
  3. 3The tool creates the result with temporary server-side processing.
  4. 4Download the output or copy the result when it is ready.

FAQ

›Why does the browser show a certificate warning?
Common causes include expired certificates, hostname mismatch, or incomplete certificate chains.
›What is a certificate chain?
It’s the sequence of certificates from your leaf certificate up to a trusted root CA.
›What are SANs?
Subject Alternative Names list the hostnames a certificate is valid for (e.g., example.com, www.example.com).
›What is ALPN?
ALPN negotiates the application protocol (like HTTP/2) over TLS during the handshake.
›Does this fix TLS issues?
No. It helps diagnose the configuration so you can adjust server/CDN settings and renew certificates correctly.