SSL Certificate Checker
Check SSL/TLS certificate validity, expiry date, issuer, and certificate chain for any domain.
What is SSL Certificate Checker?
SSL (Secure Sockets Layer) and its successor TLS (Transport Layer Security) encrypt data between browsers and servers. An SSL certificate proves a website's identity and enables the padlock in the address bar. Checking certificates helps you verify validity, track expiry, audit issuer details, and ensure Subject Alternative Names (SANs) cover all required domains. Expired or misconfigured certificates trigger browser warnings and can break HTTPS access.
This tool queries the certificate for any domain and displays the subject, issuer, validity dates, serial number, signature algorithm, key algorithm and size, and SANs. Use it before deployments, for security audits, or to monitor when certificates need renewal.
How to Use SSL Certificate Checker
- Enter a domain name (e.g.,
example.com) in the Domain field. You can pastehttps://example.com— the protocol is stripped automatically. - Click Check or press Enter in the input, or Ctrl+Enter anywhere. The tool queries the ToolCrux API and fetches certificate details.
- View the status hero (Valid, Expired, or Expiring Soon) and the structured table: Subject, Issuer, Valid From/Until, Serial Number, Signature Algorithm, Key Algorithm & Size, and SANs.
- Switch to Raw view for the full JSON. Use Copy or Save to export results.
Tips & Best Practices
Set calendar reminders 30–60 days before certificate expiry. Use automatic renewal (e.g., Let's Encrypt with certbot) when possible. Ensure SANs include all hostnames (www and non-www, subdomains). RSA 2048-bit or higher and ECDSA P-256 are considered secure. Use Ctrl+Shift+C to copy and Esc to clear. Pair this with DNS Lookup and WHOIS Lookup for a full domain audit.
When to Use This Tool
Use the SSL Certificate Checker for security audits, pre-deployment checks, and ongoing monitoring. Verify certificates after issuance or migration, audit third-party domains before integration, and monitor expiry for all production domains. Combine with HTTP Headers Checker for full security posture.
Frequently Asked Questions
What is an SSL certificate?
An SSL certificate is a digital credential that verifies a website's identity and enables encrypted HTTPS connections. It binds a public key to the domain name and is issued by a trusted Certificate Authority (CA).
How do I check if a website has a valid SSL certificate?
Use this SSL Certificate Checker: enter the domain name and click Check. You'll see the validity period, issuer, key size, and Subject Alternative Names. A lock icon in the browser address bar also indicates HTTPS.
What happens when an SSL certificate expires?
When an SSL certificate expires, browsers show security warnings and visitors may be unable to access the site over HTTPS. Browsers block expired certificates to protect users from potential man-in-the-middle attacks.
What is the difference between SSL and TLS?
SSL (Secure Sockets Layer) is the older protocol; TLS (Transport Layer Security) is its successor. TLS 1.2 and 1.3 are the current standards. People often say "SSL" when they mean TLS.
What does the certificate chain contain?
The certificate chain includes the server certificate, intermediate CA certificates, and the root CA certificate. Browsers verify the chain to establish trust from a trusted root to your domain.
How often should I check my SSL certificate?
Check your certificate periodically, especially 30–60 days before expiry. Set calendar reminders or use monitoring tools to avoid unexpected expirations. Most certificates are valid for 90 days to 13 months. Try our DNS Lookup or WHOIS Lookup for related checks.