Network & web
SSL Certificate Checker
Inspect the TLS certificate, issuer, expiry date, SANs, protocol, and cipher for a public HTTPS host.
Public hostnames only. The checker connects to port 443 and blocks local/private targets.
How to use this tool
Enter a public HTTPS hostname, for example `lumio.pw`.
Run the check to inspect the certificate issuer, validity dates, SAN names, protocol, cipher, and SHA-256 fingerprint.
Use the result to catch expiry risk, hostname mismatch, or unexpected certificate changes.
What the certificate check shows
The certificate subject and issuer help identify which certificate authority issued the certificate.
The validity dates show when the certificate starts and expires.
Subject Alternative Names, or SANs, show which hostnames the certificate is valid for.
Common TLS problems
Expired certificates usually break browser trust immediately and can block real users from reaching the site.
Hostname mismatch happens when the certificate does not include the exact host being checked.
A valid certificate does not prove the whole application is secure; it only confirms part of the encrypted transport setup.
Security limits of an online checker
This tool checks a public host from the Lumio server, so it reflects what the server can see from the internet.
It cannot inspect private intranet hosts, client-side certificate prompts, or every regional CDN edge.
Use monitoring in production if certificate expiry would cause downtime.
Examples
Check an apex domain
The checker connects to port 443 and reports the certificate details visible for that host.
Inputexample.com
Check a subdomain separately
A certificate can be valid for one host and not another, so check the exact hostname users open.
Inputwww.example.com
FAQ
What is a SAN on an SSL certificate?
SAN means Subject Alternative Name. It lists the DNS names that the certificate is valid for, such as `example.com` and `www.example.com`.
How early should I renew a certificate?
Renew well before expiry. Automated ACME setups often renew around 30 days before expiration, which leaves time to catch failures.
Does a valid TLS certificate mean the site is safe?
No. TLS protects transport and identity for the hostname. Application security still depends on the code, configuration, authentication, and data handling.
Can this check private local hosts?
No. The checker is intended for public HTTPS hosts and should not be used for private network targets.