SSL Certificate Checker
Verify certificate expiration date, issuer CN/O details, validity status, and remaining days for a secure HTTPS server.
Configure inputs and click Run
How It Works & Educational Guide
How Nexifr's SSL Certificate Checker handles your data securely in the browser — covering supported formats, encoding standards, and practical developer workflows.
01What is an SSL/TLS Certificate?
An SSL (Secure Sockets Layer) or TLS (Transport Layer Security) certificate is a digital credential that encrypts communication between a user's browser and a web server. It protects passwords, access tokens, and payment information from being intercepted by attackers on the network.
02Why SSL Expirations are Critical to Monitor
SSL certificates are valid for a maximum of 397 days. If a certificate expires, web browsers display a prominent warning screen ('Your connection is not private'). This warning causes visitors to leave, damages user trust, increases bounce rates, and lowers your search ranking.
03Verifying Certificate Issuers and SANs
A valid certificate must be issued by a trusted Certificate Authority (CA) recognized by browser vendors. Our checker performs socket inspections to verify the certificate path, the expiration timeline, and the Subject Alternative Names (SAN) list to ensure the certificate covers all subdomains.
Frequently Asked Questions
Why should I check my SSL certificate?
Web browsers flag expired or invalid SSL certificates as insecure — displaying a full-page 'Your connection is not private' warning that causes visitors to immediately leave. Checking your SSL certificate status helps you renew before expiry, verify correct domain matching, and ensure browsers and search engines trust your site.
How do I check if an SSL certificate is valid?
Enter your domain name (e.g. github.com) in the field above and click Run. The tool connects to your server and retrieves the certificate details including the issuer, expiration date, remaining days, and whether the domain name matches the certificate's Common Name (CN) or Subject Alternative Name (SAN) — all in under a second.
What is an SSL certificate checker tool?
An SSL certificate checker is a tool that connects to a web server and reads its TLS certificate details without a browser. It reveals expiration dates, the Certificate Authority (CA) that issued it, the number of days remaining before renewal is required, and whether the certificate is properly configured for the queried domain.
How often should I check SSL certificates?
Best practice is to check your SSL certificates at least once a month, and set up automated renewal alerts 30 and 7 days before expiry. Free certificates from Let's Encrypt expire every 90 days — missing renewal causes your site to become inaccessible to all browsers.
Does HTTPS affect Google search rankings?
Yes. Google confirmed HTTPS as a ranking signal in 2014. Sites without a valid SSL certificate may rank lower than equivalent HTTPS sites. Beyond rankings, browsers like Chrome actively warn users about non-HTTPS pages, dramatically increasing bounce rates and reducing time-on-site signals.