SSL Checker
Verify SSL/TLS certificate validity, chain of trust, and expiry for any domain.
Checks the live TLS handshake and certificate served by the domain. Results show issuer, expiry, SAN entries, and protocol version.
Why SSL Certificates Matter for Security and SEO
An SSL (Secure Sockets Layer) or, more accurately, TLS (Transport Layer Security) certificate is a small digital file that binds a domain name to a cryptographic key. When a browser connects to a website over HTTPS, the server presents this certificate so the browser can verify that it is talking to the genuine server and not an impersonator. The certificate also enables the encryption that keeps passwords, payment details, and personal data private in transit. Without a valid certificate, modern browsers flag the site as "Not Secure," warn users away, and in some cases block the connection entirely.
Beyond security, SSL has become a baseline requirement for search engine optimization. Google has used HTTPS as a lightweight ranking signal since 2014, and browsers like Chrome now display prominent warnings on HTTP pages that collect form data. An expired, misconfigured, or untrusted certificate does not just break trust — it actively harms your visibility and conversion rate. Certificate outages are one of the most common causes of unplanned website downtime, often caused by auto-renewal failures or missing intermediate certificates in the chain of trust.
Regularly checking your SSL certificate helps you catch problems before your users do. This free SSL checker retrieves the live certificate served by any domain and reports its validity status, issuing authority, expiry date, days remaining, the negotiated TLS protocol version, and all Subject Alternative Names (SAN). Use it to verify a fresh installation, monitor an upcoming renewal, audit a subdomain, or diagnose a "connection not private" error reported by a visitor.
How to Use the SSL Checker
- Enter your domain name (for example,
example.com) into the input field. The tool connects on port 443, so no protocol prefix is needed. - Click the Check SSL button. The tool performs a live TLS handshake against the target server and reads the presented certificate.
- Review the certificate details, including validity, issuer, expiry date, days remaining, protocol version, and SAN entries. Color coding shows green (healthy), yellow (renew soon), or red (expired or invalid).
Key SSL Concepts You Should Know
Understanding a handful of core concepts makes certificate troubleshooting far easier. The four concepts below cover the vast majority of issues you will encounter.
Certificate Validity
Every certificate has a notBefore and notAfter date. It is only valid within that window. Browsers reject certificates that are expired or not yet active, displaying date-related errors.
Chain of Trust
The path from your leaf certificate through intermediate certificates to a trusted root. A missing intermediate is the most common cause of "certificate not trusted" errors on desktop and mobile clients.
SAN (Subject Alternative Names)
The list of hostnames a single certificate covers. Modern certificates rely on SAN entries rather than the Common Name field. A mismatch between the requested hostname and a SAN entry causes a name validation error.
TLS Protocol Version
The protocol used for the encrypted handshake. TLS 1.3 is the current best practice; TLS 1.2 is still acceptable. TLS 1.0 and 1.1 are deprecated and should be disabled because they have known vulnerabilities.
Frequently Asked Questions
How do I renew my SSL certificate?
Renew through your Certificate Authority (CA) or hosting provider before the expiry date. If using Let's Encrypt, certificates auto-renew via the ACME protocol every 60 days. Most CAs send email reminders 30, 14, and 7 days before expiry.
How can I get a free SSL certificate?
Let's Encrypt offers free SSL certificates trusted by all major browsers. Use Certbot, acme.sh, or your hosting provider's built-in integration. Cloudflare also provides free SSL edge certificates.
What is a certificate chain?
A certificate chain is the path from your server certificate (leaf) through one or more intermediate certificates to a trusted root certificate. If intermediate certificates are missing, browsers show "certificate not trusted" errors even when your certificate is valid.
What happens when my certificate expires?
Browsers display security warnings (NET::ERR_CERT_DATE_INVALID), users see "Your connection is not private", and HTTPS connections may fail entirely. Search engines may downgrade your rankings. Renew immediately to restore trust.
What TLS version should I use?
TLS 1.3 is recommended for new deployments (faster handshake, stronger security). TLS 1.2 is still acceptable and widely supported. Disable TLS 1.0 and 1.1 as they have known vulnerabilities. Check your server's SSL configuration with this tool.