SSL Certificate Checker
Check an SSL/TLS certificate online: expiration date, issuer, CN, SAN, self-signed certificate status and common HTTPS configuration issues.
SSL/TLS Checker Online
Analyze a domain and check the status of its SSL/TLS certificate. Review the expiration date, issuer, Common Name (CN), Subject Alternative Names (SAN), negotiated TLS version, cipher, and common signs of misconfiguration.
This tool is useful for system administrators, web developers, technical SEO professionals, and anyone who needs to quickly validate the HTTPS security of a website.
What does this SSL/TLS checker test?
The tool tries to establish a secure connection with the selected host and retrieve the certificate presented by the server. It then shows the key data you need to verify whether the site is properly configured and whether the certificate is still valid.
- Certificate start and expiration dates
- Days remaining before expiry
- Certificate issuer
- Common Name (CN)
- SHA-256 and SHA-1 fingerprint
- Subject Alternative Names (SAN)
- Self-signed certificate detection
- Hostname match against certificate names
- Negotiated TLS version and cipher
- HTTP to HTTPS redirection
Why check a website SSL certificate?
An expired, incorrectly issued, or badly installed SSL/TLS certificate can trigger browser warnings, reduce trust, hurt conversions, and cause problems in technical audits. It can also affect external tools that monitor availability, security, or HTTPS compliance.
With this checker, you can quickly detect whether a domain has a certificate close to expiration, whether the hostname does not match the certificate, whether the negotiated TLS version is not what you expect, or whether the HTTPS redirect is not properly configured.
Common use cases
Check HTTPS issues that can affect crawling, trust, redirects, and user experience.
Validate certificates in production, staging, or domain-exposed services.
Make sure the issued certificate properly covers the main domain and subdomains.
Frequently asked questions
What is an SSL/TLS certificate?
It is a digital certificate that encrypts the connection between the browser and the server and helps identify the domain being served securely over HTTPS.
What does it mean if a certificate is expired?
It means the certificate validity period has ended. Browsers usually show security warnings, and users may leave the site because they no longer trust the connection.
What are CN and SAN?
CN stands for Common Name, the traditional certificate name field. SAN stands for Subject Alternative Names, which are now the most important field for declaring which domains and subdomains a certificate covers.
What is a self-signed certificate?
It is a certificate issued by the same entity that uses it, without a trusted public certificate authority. It may be valid for internal environments, but it usually triggers warnings in browsers and public services.
Can I use this tool for any domain?
Yes, as long as the host is public and responds on the selected port. For safety reasons, internal, private, or reserved hosts should not be analyzed.