LuabifyQuick device diagnostics

SSL Certificate Checker: Check Expiry, SANs, Issuer & Hostname Match

Click SSL certificate checker Inspect certificate expiry, issuer, hostname match, SAN coverage, protocol, and fingerprint for a public HTTPS endpoint.

TLS certificate

SSL Certificate Checker

Check expiry, issuer, SANs, protocol, and hostname match for any public HTTPS host.

Ready

This tool performs a server-side TLS handshake to read the certificate presented by the host.

Certificate results

Run a check to see certificate details.

Certificate statusNo certificate checked yet

Certificate details will appear here after a successful check.

Why run an SSL certificate checker online

An SSL certificate checker online helps you confirm which certificate a public HTTPS endpoint is actually presenting right now. That matters after certificate renewals, CDN or proxy changes, DNS cutovers, load balancer updates, and whenever browsers or monitoring tools start reporting HTTPS warnings, hostname mismatch, or expiry risk.

How the test runs

The tool performs a server-side TLS handshake against the target hostname or HTTPS URL and reads the certificate returned by that endpoint. It extracts key details such as issuer, subject, common name, SAN coverage, validity dates, days remaining, hostname match, protocol, serial number, and SHA-256 fingerprint so you can inspect the exact certificate currently exposed.

How to interpret results

Start with validity dates, hostname match, SAN list, and issuer. If the certificate is expired, expiring soon, or does not match the hostname you checked, browsers and clients may show TLS warnings even if the service is otherwise online. SANs help confirm which hostnames are actually covered, while protocol, fingerprint, and serial number help you verify that the endpoint is serving the specific certificate you expected through a CDN, reverse proxy, or direct origin.

  • Expired means the certificate is already outside its valid time window.
  • Expiring soon means renewal should be handled before users or monitoring systems start failing.
  • Hostname mismatch means the certificate does not properly cover the host you tested.
  • SAN coverage helps confirm whether subdomains, www variants, or alternate hostnames are included.
  • Fingerprint and serial number help verify whether the endpoint is serving the exact certificate you expected.

This check reports the certificate returned during the TLS handshake. It does not perform a full SSL Labs style audit, grade ciphers, inspect HSTS, verify redirect behavior, or reveal private keys or server configuration.

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Frequently Asked Questions

What does this SSL certificate checker show?

It shows the certificate currently presented by a public HTTPS endpoint during the TLS handshake. You can review validity dates, issuer, subject, SAN coverage, hostname match, protocol, serial number, and fingerprint.

How does the SSL certificate checker work?

The tool performs a server-side TLS handshake to the host you enter and reads the certificate returned by that endpoint. It then formats the main certificate fields so you can review what is actually being served right now.

Can I enter a full HTTPS URL instead of just a hostname?

Yes. You can enter a hostname or a full HTTPS URL, and the checker will extract the host before testing the endpoint. The focus is the certificate served for that public HTTPS target.

What does hostname match mean in an SSL certificate check?

Hostname match means the certificate covers the host you tested through its common name or SAN entries. If it does not match, browsers and API clients may warn that the certificate belongs to a different name.

Why can a certificate look valid but still trigger HTTPS errors?

A certificate can still cause problems because of hostname mismatch, incomplete or incorrect deployment, local trust issues, or edge and origin certificate confusion. Valid dates alone do not guarantee a clean HTTPS setup.

What are SANs in an SSL certificate?

SANs, or Subject Alternative Names, are the hostnames the certificate is allowed to secure. They are critical for checking whether www variants, subdomains, or alternate hostnames are actually covered.

Can this tool tell me if a certificate is about to expire?

Yes. It calculates the remaining validity window and surfaces whether the certificate is already expired or nearing expiry. That helps you plan renewals before customer-facing TLS failures begin.

What do fingerprint and serial number help confirm?

They help confirm whether the endpoint is serving the exact certificate you expected after a renewal, CDN update, reverse proxy change, or cutover. They are especially useful when several systems could be serving different certificates.

Can this SSL certificate checker test private or internal hosts?

No. This checker is intended for public HTTPS endpoints reachable from the service. Private, local, or internal-only network targets are not the goal of this tool.

Is this SSL certificate checker safe to use?

Yes. It only reads certificate data exposed during the TLS handshake. It does not request private credentials, access server files, or modify the remote service.

What can this SSL certificate checker not verify?

It does not perform a full TLS security audit with cipher grading, HSTS evaluation, OCSP analysis, redirect testing, or broader application security checks. It is focused on the certificate presented by the endpoint.

When should I use this SSL certificate checker online?

Use it after certificate renewal, CDN or proxy changes, DNS migrations, origin swaps, or whenever HTTPS warnings appear in browsers, monitoring systems, or API clients. It is one of the fastest first checks for certificate deployment problems.