Free SSL / TLS Certificate Checker
Test SSL/TLS certificate validity, verify Certificate Authority (CA) issuers, monitor expiration countdown, and audit TLS protocols and SANs.
Enter Domain Name
Type your website hostname (e.g. mysite.com) without https.
TLS Handshake Inspection
Our server connects to port 443 and reads the X.509 certificate.
Detailed Security Report
Inspect expiration days, trusted status, SANs, and protocol version.
Track exact days remaining before renewal is required.
Verify Let's Encrypt, Cloudflare, DigiCert, or Sectigo CAs.
Ensure modern TLSv1.3 and secure ciphers are active.
Inspect all alternative domains protected by the cert.
- Set up automatic renewals (such as certbot or Cloudflare SSL) at least 30 days before certificate expiry.
- Ensure your server forces modern TLSv1.2 and TLSv1.3, disabling deprecated SSLv3 and TLSv1.0 protocols.
- Check that your root and intermediate certificate chains are correctly bundled to prevent mobile browser errors.
Frequently Asked Questions about SSL & TLS
Helpful answers to common questions about checking username availability, domain extensions, and registration.
What is an SSL/TLS certificate and why is it required?
SSL (Secure Sockets Layer) and TLS (Transport Layer Security) encrypt the communication channel between a user's web browser and the web server. They prevent eavesdropping, data tampering, and man-in-the-middle attacks.
How does this free SSL Checker test certificates?
Our tool opens a native Node.js TLS socket connection to port 443 of the target host, extracts the peer certificate chain, verifies expiry dates, cipher suites, protocol versions (e.g. TLSv1.3), and inspects Subject Alternative Names (SANs).
What happens if an SSL certificate expires?
Browsers display a prominent 'Your connection is not private' security warning (NET::ERR_CERT_DATE_INVALID), blocking most visitors from accessing the site and degrading organic search rankings.
What are Subject Alternative Names (SANs)?
SANs allow a single SSL certificate to secure multiple domain names and subdomains (e.g. example.com, www.example.com, api.example.com) under one unified cryptographic cert.