SSL Certificate Checker
Check an SSL/TLS certificate online: expiration date, issuer, CN, SAN, self-signed certificate status and common HTTPS configuration issues.
SSL Certificate Checker
Analyze a domain and review the status of its SSL/TLS certificate. Check the expiration date, issuer, Common Name (CN), Subject Alternative Names (SAN), and common signs of SSL misconfiguration.
This tool is useful for system administrators, developers, technical SEO professionals, and anyone who needs to validate a website’s HTTPS security quickly.
What does this SSL certificate checker analyze?
The tool tries to establish a secure connection with the specified host and retrieve the certificate presented by the server. It then shows essential details to validate whether the site is correctly configured and whether the certificate is still valid.
- Certificate start date and expiration date
- Remaining days before expiration
- Certificate issuer
- Common Name (CN)
- Subject Alternative Names (SAN)
- Self-signed certificate detection
- Host and certificate name matching
- Warnings and practical recommendations
Why check a website’s SSL certificate?
An expired, wrongly issued, or incorrectly installed SSL/TLS certificate can trigger browser warnings, reduce trust, hurt conversions, and create issues during technical audits. It can also affect external monitoring tools and HTTPS compliance checks.
With this checker you can quickly identify whether a domain has a certificate close to expiration, whether the host name does not match the certificate, or whether SAN coverage is incomplete.
Common use cases
Check HTTPS issues that may impact crawling, trust, and user experience.
Validate certificates in production, staging, or other public services exposed by domain.
Verify that the issued certificate properly covers the main domain and required 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 identifies 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 display security warnings, and users may leave the site because they no longer trust the connection.
What are CN and SAN?
The CN is the traditional Common Name field of the certificate. SAN are the alternative names supported by the certificate, and today they are the most important field for defining which domains and subdomains are covered.
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 can be valid in internal environments, but it causes 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 specified port. For security reasons, internal, private, or reserved hosts should not be analyzed.