Website Testing
SSL Checker: Verify Your SSL/TLS Certificate
An expired or misconfigured SSL certificate causes browser security warnings that drive users away. Our SSL checker verifies your certificate's validity, expiration date, certificate chain, TLS version, and cipher suite strength in seconds.
Launch in Mission ControlWhat It Measures
This tool checks the SSL/TLS certificate for any domain, reporting certificate validity, days until expiration, the full certificate chain, TLS protocol version (TLS 1.2 vs 1.3), cipher suite, certificate authority, and whether HSTS is enabled.
How It Works
- Connects to the server on port 443 using a TLS handshake
- Retrieves and parses the full certificate chain
- Checks each certificate against its issuing CA
- Evaluates TLS configuration quality including protocol version and cipher strength
Why It Matters
An expired SSL certificate causes all major browsers to show a red warning page, effectively taking your site offline for most users. Weak TLS versions (TLS 1.0 or 1.1) expose users to known vulnerabilities. Regular SSL monitoring prevents these issues before they impact visitors.
Understanding Your Results
Certificates should be valid with more than 30 days remaining. TLS 1.3 is preferred; TLS 1.2 is acceptable. TLS 1.0 and 1.1 are deprecated and should be disabled. HSTS should be enabled. The certificate chain should be complete with a trusted root CA.
Ready to test?
Run SSL Checker Now →Frequently Asked Questions
How often should I check my SSL certificate?
Check your SSL certificate expiry at least monthly and set up automated monitoring with email alerts when the certificate is 30 and 14 days from expiring. Many free and paid monitoring services handle this automatically. Let's Encrypt certificates expire every 90 days and should be auto-renewed.
What is a certificate chain?
The certificate chain (or chain of trust) is the sequence of certificates from your domain's certificate back to a trusted root certificate authority (CA). Intermediate certificates link your certificate to the root CA. An incomplete chain causes browser warnings even if your certificate itself is valid.
What is the difference between TLS 1.2 and TLS 1.3?
TLS 1.3 is faster (reduces handshake round trips) and more secure (removes outdated cipher suites and vulnerable features). TLS 1.2 is still widely used and secure when properly configured. TLS 1.0 and 1.1 are deprecated by all major browsers and should be disabled.
What is HSTS?
HTTP Strict Transport Security (HSTS) is a header that tells browsers to always use HTTPS for your domain, even if someone types http://. This prevents SSL stripping attacks where an attacker intercepts the initial HTTP request before redirection. Enabling HSTS with a long max-age is considered a security best practice.
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