SSL/TLS Certificate Checker

Enter a domain to inspect its HTTPS certificate: issuer, validity period, certificate chain, and SAN domains.

SSL/TLS Certificates: How They Work and Why Regular Checks Matter

1. What Is an SSL/TLS Certificate?

SSL (Secure Sockets Layer) and its successor TLS (Transport Layer Security) form the backbone of encrypted internet communication. When your browser shows a padlock icon in the address bar, it means data between you and the server is encrypted via TLS. An SSL/TLS certificate is a digital file issued by a trusted Certificate Authority (CA) that binds a domain name to a cryptographic key, ensuring you are communicating with the authentic server rather than a man-in-the-middle attacker.

2. Why Should You Check Certificates Regularly?

Certificate expiration is one of the most common causes of unexpected website outages. When an SSL certificate expires, browsers display a prominent security warning that blocks visitors from proceeding. For e-commerce sites or SaaS platforms, even a few minutes of certificate downtime can result in significant revenue loss and eroded user trust. Additionally, misconfigured certificate chains (missing intermediate CA certificates) can trigger warnings in certain browsers or operating systems.

Using the ipinfo.im SSL checker, you can quickly retrieve the remaining validity period, issuer details, and SAN (Subject Alternative Name) domain list, allowing you to take proactive action before problems occur.

3. How to Read the Certificate Report

  • Common Name (CN): The primary domain the certificate was issued for. Wildcard certificates typically appear as *.example.com.
  • Issuer: The CA that signed the certificate. Popular CAs include Let's Encrypt, DigiCert, and Sectigo.
  • Validity Period: The start and end dates. Let's Encrypt certificates are valid for 90 days; commercial certificates are typically valid for 1 year.
  • SAN List: All domains covered by the certificate. A single certificate can protect multiple subdomains and even entirely different domain names.

4. Common SSL Issues and Troubleshooting

Certificate expiry is not the only SSL failure scenario. Other common issues include: domain mismatch (the visited domain is not listed in CN or SAN), incomplete certificate chains caused by missing intermediate certificates, and servers still using deprecated TLS 1.0/1.1 protocol versions. Combine this tool with our DNS Resolution and HTTP Header Inspection tools for a comprehensive HTTPS configuration audit.