SSL Certificate Checker - Verify HTTPS Status
How to Use the SSL Certificate Checker
Enter a domain name (without https://) and click Check. The tool tests the HTTPS connection to the domain and reports the certificate status, issuer, and whether the connection is secure. The check takes just a few seconds and provides a clear pass or fail result.
Why SSL/TLS Certificates Matter
SSL/TLS certificates serve two critical functions: they encrypt the connection between a user’s browser and the web server, preventing eavesdropping on sensitive data, and they authenticate the server’s identity, proving that users are communicating with the legitimate website and not an impersonator.
What an SSL Certificate Contains
Every SSL certificate includes several pieces of information that browsers verify before establishing a secure connection:
| Field | Description | Example |
|---|---|---|
| Subject | Domain name the certificate covers | example.com |
| Issuer | Certificate Authority that issued it | Let’s Encrypt, DigiCert |
| Valid From | Date the certificate became active | 2026-01-01 |
| Valid Until | Expiration date | 2026-04-01 |
| Key Size | Encryption key strength | 2048 or 4096 bits (RSA) |
| Signature Algorithm | Hash algorithm used | SHA-256 with RSA |
Certificate Validation Chain
Browsers verify SSL certificates through a chain of trust. Your certificate is signed by an intermediate Certificate Authority (CA), which is signed by a root CA that the browser inherently trusts. If any link in this chain is broken, missing, or expired, the browser rejects the certificate and shows a security warning.
Common SSL Certificate Issues
Expired Certificates
Certificate expiration is the most common SSL issue. Let’s Encrypt certificates are valid for 90 days, while traditional CA certificates last one year. Automated renewal tools like Certbot prevent expirations, but misconfigurations can cause renewals to fail silently.
Domain Mismatch
A certificate issued for example.com does not cover www.example.com unless it includes that subdomain as a Subject Alternative Name (SAN) or uses a wildcard certificate (*.example.com). Domain mismatch errors occur when the URL in the browser does not match any name on the certificate.
Incomplete Certificate Chain
If the server does not send the intermediate certificate alongside the main certificate, some browsers (especially mobile browsers) cannot complete the chain of trust and reject the connection. This results in errors on some devices but not others, making it a tricky issue to diagnose.
Mixed Content Warnings
Even with a valid certificate, loading images, scripts, or stylesheets over HTTP (instead of HTTPS) on an HTTPS page triggers mixed content warnings. Browsers may block these insecure resources entirely, breaking page functionality.
SSL/TLS Protocol Versions
| Version | Status | Notes |
|---|---|---|
| SSL 2.0 | Deprecated | Severe vulnerabilities, disabled everywhere |
| SSL 3.0 | Deprecated | Vulnerable to POODLE attack |
| TLS 1.0 | Deprecated | Removed from major browsers in 2020 |
| TLS 1.1 | Deprecated | Removed from major browsers in 2020 |
| TLS 1.2 | Active | Widely supported, considered secure |
| TLS 1.3 | Active | Fastest, most secure, recommended |
Modern servers should support TLS 1.2 and TLS 1.3 while disabling all older protocols. TLS 1.3 provides improved security and faster handshakes with fewer round trips.
Monitoring and Automation
Do not rely on manual checks alone. Set up automated monitoring that alerts you before certificates expire. Most hosting providers and CDNs offer automatic certificate renewal. For custom setups, tools like Certbot automate Let’s Encrypt certificate renewal.
For checking the HTTP security headers your server returns after verifying SSL, use the HTTP Header Inspector. To verify that your domain’s DNS records are correctly configured, the DNS Lookup tool checks A, MX, and TXT records.
Related Tools
- HTTP Header Inspector - Check security headers after verifying SSL
- DNS Lookup - Verify domain DNS configuration
- Text Encryptor - Encrypt sensitive text with AES-256
Frequently Asked Questions
How do I check if a website has a valid SSL certificate?
Enter the domain name in this tool and click Check. The tool tests the HTTPS connection and reports whether the certificate is valid, who issued it, and when it expires. A valid certificate means the connection between users and the server is encrypted.
What happens when an SSL certificate expires?
When a certificate expires, browsers display a full-page security warning that most visitors will not bypass. This effectively takes your website offline for visitors. Search engines may also temporarily derank sites with expired certificates. Regular monitoring prevents unexpected expirations.
What is the difference between SSL and TLS?
SSL (Secure Sockets Layer) is the predecessor to TLS (Transport Layer Security). All modern 'SSL' certificates actually use TLS 1.2 or 1.3 for encryption. The term 'SSL' persists in common usage even though the actual SSL protocols have been deprecated due to security vulnerabilities.
Do I need an SSL certificate for my website?
Yes. All modern websites should use HTTPS. Beyond security, Google uses HTTPS as a ranking signal, browsers mark HTTP sites as 'Not Secure,' and many web APIs (like geolocation and service workers) require HTTPS to function. Free certificates are available from Let's Encrypt.