What is an SSL certificate and why is it important?

An SSL (Secure Sockets Layer) certificate encrypts data between a user's browser and a website, ensuring that sensitive information like passwords and credit card numbers cannot be intercepted. It also verifies that the website is genuine, building trust with visitors.

How does this SSL checker work?

The tool connects to the specified domain over a secure TLS handshake, retrieves the certificate chain, and parses its fields. Key details such as expiry date, issuer, SANs, and signature algorithm are extracted and displayed.

Is my data secure when using this SSL checker?

Yes. All processing occurs entirely in your browser using standard Web Crypto APIs and secure TLS connections. No domain data is stored or logged on our servers — the tool is 100% private.

What is a Subject Alternative Name (SAN)?

A Subject Alternative Name (SAN) is a field in an SSL certificate that lists additional domains or subdomains covered by the same certificate. SANs are essential for modern certificates, allowing one certificate to secure multiple hostnames.

What does a valid SSL certificate expiry date look like?

A valid certificate typically expires after 1–2 years. The date is displayed in UTC format. If the expiry date is in the past, the certificate is no longer valid and should be renewed immediately to avoid security warnings.

Are there any limitations to this free SSL checker?

The tool is completely free with no usage limits. It works with any publicly accessible domain. For domains behind strict firewalls or on internal networks, the tool may not be able to establish a connection. All processing is local and private.

Free SSL Checker — Verify SSL/TLS Certificate & Expiry Online

Check any domain's SSL/TLS certificate details instantly. Verify the expiry date, issuer,Subject Alternative Names (SANs), and signature algorithm. All processing is client-side and private — no signup or upload required.

Quick Answer

How do I check an SSL certificate for free?

Enter the domain name, click 'Check SSL', and the tool will display certificate details including expiry, issuer, SANs, and signature algorithm. All processing happens in your browser with no data sent to servers.

Security Utility

Free SSL Certificate Checker

Verify the security, validity, and expiration date of any website's SSL/TLS certificate instantly.

Domain Verification

Website URL or Domain Name

What to check beyond "is it valid"

A certificate can be valid but still cause browser warnings or downtime. The five things to verify after issuing or renewing a cert:

Domain matchThe certificate's Subject Alternative Names (SANs) must exactly match the domain being served — including or excluding www. A cert for example.com does not cover www.example.com unless listed separately or a wildcard cert is used.
Certificate chainThe server must send the complete chain: leaf cert + intermediate CA cert(s). A missing intermediate causes browser warnings on some clients even if the root CA is trusted. This is the most common misconfiguration after cert renewal.
Expiry dateLet's Encrypt certificates expire every 90 days. Commercial certs typically 1–2 years. Set a monitoring alert at 30 days before expiry — browsers start showing "Not Secure" warnings when expiry is near.
Protocol and cipherTLS 1.0 and 1.1 are deprecated and cause browser warnings in Chrome and Firefox. Your server should offer TLS 1.2 minimum; TLS 1.3 is preferred for performance (1 round-trip handshake vs. 2 for TLS 1.2).

How to monitor expiry automatically

Manual checks miss renewals. Set up automated monitoring: most uptime monitoring services (UptimeRobot, Better Uptime, Checkly) include SSL expiry checks. Alternatively, run a cron job using openssl s_client -connect example.com:443 | openssl x509 -noout -dates and alert when the expiry date is within 30 days. For Let's Encrypt with Certbot, auto-renewal is enabled by default via a systemd timer or cron — verify it's running with certbot renew --dry-run.

Video demo

☕ Support Us

What to check beyond "is it valid"

How to monitor expiry automatically

Related network tools