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Home / Network Tools / SSL Checker

SSL Checker

Check the SSL/TLS certificate of any domain � view issuer details, validity period, SANs, protocol support, cipher suites, and the overall security grade. Ensure your website is secure and trusted.

Enter a domain without https://. Examples: google.com, github.com, example.org
Check Failed

Unable to analyze the SSL certificate for this domain. Please verify the domain name and try again.

Recent Checks

No checks yet. Enter a domain above and click "Check SSL".
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How to Use the SSL Checker Tool

1

Enter a Domain

Type any domain name (e.g. google.com, github.com) into the input field above. You can enter the domain with or without "www" � the tool checks both. Do not include "https://" or paths.

2

Click Check SSL

Press the "Check SSL" button or hit Enter. The tool queries the mate.tools SSL API to perform a comprehensive analysis of the domain's SSL/TLS certificate and security configuration.

3

Review the Results

View the complete SSL report including security grade, certificate issuer, validity dates, SANs, TLS protocol support, cipher suites, certificate chain, and more. Copy all data or recheck anytime.

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About the SSL Checker Tool

The FreeNestTools SSL Checker is a free, browser-based tool that performs a comprehensive analysis of any domain's SSL/TLS certificate and security configuration. It uses the mate.tools SSL API � a reliable CORS-enabled API � to provide accurate, detailed, and actionable results directly in your browser.

SSL/TLS certificates are the foundation of web security. They encrypt communications between your browser and the web server, ensuring that sensitive data such as passwords, credit card numbers, and personal information remains private and tamper-proof. A properly configured SSL certificate is essential for establishing trust, protecting user data, improving SEO rankings, and meeting regulatory compliance requirements such as GDPR, PCI-DSS, and HIPAA.

Who Should Use This Tool

This SSL Checker is designed for website owners, system administrators, DevOps engineers, security researchers, web developers, and IT professionals. Use it to verify that your own domains have valid, properly configured certificates; to check third-party domains before integrating with their services; to troubleshoot SSL-related issues; to ensure compliance with security policies; and to maintain trust with your visitors.

What We Check

Our tool analyzes certificate details (subject, issuer, validity period, serial number, signature algorithm), Subject Alternative Names (SANs) � all domains the certificate covers, TLS protocol support (TLS 1.0, 1.1, 1.2, 1.3), cipher suite strength, certificate chain completeness, key exchange methods, and assigns an overall security grade (A through F) based on protocol version, cipher strength, and certificate validity. We also check whether the domain supports HTTPS.

Before checking SSL, use the Website Status Checker to confirm the site is online. Regular SSL checking is a critical maintenance task. Certificates expire � typically after 90 days to 1 year � and an expired certificate will cause browsers to display security warnings that drive visitors away. Misconfigurations, weak cipher support, or incomplete certificate chains can also compromise security even when the certificate itself is technically valid. We recommend checking your SSL configuration at least monthly, and immediately after any certificate renewal or server configuration change.

Privacy & Data Handling

When you enter a domain, the domain name is sent to the mate.tools SSL API for analysis. This is necessary to perform the certificate check. We do not store, log, cache, or share the domains you search. No personal information is collected or transmitted. All results are displayed in your browser and are discarded when you close or refresh the page. There are no registration requirements, no API keys, and no usage limits.

Accuracy & Limitations

The mate.tools SSL API performs real-time certificate checks by connecting to the domain's HTTPS endpoint. Analysis typically completes within a few seconds depending on server configuration and network conditions. Some domains may have security measures (e.g., WAF, rate limiting, IP blocking) that prevent complete analysis. Results reflect the configuration at the time of testing and may not account for load-balanced environments with multiple backend servers using different configurations. The tool tests the default HTTPS endpoint (port 443) and does not scan non-standard ports.

Frequently Asked Questions

An SSL (Secure Sockets Layer) certificate is a digital certificate that authenticates a website's identity and enables an encrypted connection between a web browser and a web server. It is important because it protects sensitive data (passwords, credit card numbers, personal information) from interception by attackers, verifies that visitors are connecting to the legitimate website and not an imposter, builds trust with users through visual indicators like the padlock icon, and is required for compliance with security standards such as PCI-DSS. Additionally, Google uses HTTPS as a ranking signal, meaning SSL-secured websites often rank higher in search results.

SSL (Secure Sockets Layer) and TLS (Transport Layer Security) are cryptographic protocols that secure internet communications. TLS is the successor to SSL. SSL version 2.0 was released in 1995, followed by SSL 3.0 in 1996. TLS 1.0 (essentially SSL 3.1) was released in 1999. TLS 1.1 came in 2006, TLS 1.2 in 2008, and TLS 1.3 in 2018. SSL 2.0 and 3.0 are deprecated due to serious security vulnerabilities (including POODLE and DROWN attacks). TLS 1.0 and 1.1 are also deprecated by all major browsers. Today, TLS 1.2 and TLS 1.3 are the only secure, recommended protocols. Despite the technical evolution, the term "SSL" is still widely used to refer to both protocols.

You should check your SSL certificate: at least once a month to ensure it hasn't expired and is properly configured; immediately after renewal or reissuance to verify the new certificate is correctly installed; after any server configuration change (web server updates, new load balancers, CDN changes); before any major event (product launch, marketing campaign, traffic spike); and whenever you receive browser security warnings or user reports about connection issues. Early detection of certificate issues prevents costly downtime and loss of visitor trust.

The SSL grading system evaluates certificate configuration and security: A (Excellent) � strong security with modern protocols (TLS 1.3) and strong ciphers; B (Adequate) � acceptable security but with older protocol versions or weaker ciphers; C (Mediocre) � significant weaknesses that should be addressed; D (Poor) � serious security concerns; F (Failed) � expired, invalid, or untrusted certificate. For production websites, a grade of A or higher is strongly recommended.

Subject Alternative Names (SANs) are additional domain names listed on a single SSL certificate that are also secured by that certificate. For example, a SAN certificate might cover example.com, www.example.com, shop.example.com, mail.example.com, and api.example.com � all under one certificate. SANs are essential because modern browsers require certificates to match the exact domain in the address bar. Without the correct SAN entry, visitors will see a hostname mismatch warning even if the certificate is otherwise valid. SAN certificates are the modern alternative to legacy wildcard certificates (which only cover *.example.com) and allow up to 100+ domains on a single certificate. Our SSL Checker lists all SANs on the certificate so you can verify that every required subdomain is properly covered.

As of September 2020, the maximum validity period for SSL/TLS certificates is 397 days (about 13 months) under industry guidelines from the CA/Browser Forum. This was reduced from the previous maximum of 27 months to improve security by ensuring certificates are renewed more frequently. Some certificate authorities offer shorter validity periods of 90 days as a best practice for enhanced security and to encourage automation of certificate management through protocols like ACME (used by Let's Encrypt). When you use our SSL Checker, we show you the exact expiry date and the number of days remaining so you never miss a renewal deadline.

HSTS (HTTP Strict Transport Security) is a security policy mechanism that tells browsers to only communicate with a website over HTTPS, never over unencrypted HTTP. When a website implements HSTS, the browser automatically converts all HTTP links to HTTPS before making the request, eliminating the risk of man-in-the-middle attacks during initial HTTP connections. HSTS is required to achieve an A+ SSL grade. It is configured through the Strict-Transport-Security HTTP response header and includes a max-age directive that controls how long the browser remembers the policy. Preloading (submitting your domain to browser HSTS preload lists) provides the strongest protection but requires careful planning since it is difficult to reverse.

For optimal security and compatibility, you should support TLS 1.2 and TLS 1.3 only. TLS 1.3 is the latest protocol version (finalized in 2018) and offers significant improvements in security, performance (reduced latency with 0-RTT), and privacy (encrypted handshake). TLS 1.2 is still widely used and provides solid security when properly configured with strong cipher suites. TLS 1.0 and TLS 1.1 are deprecated by all major browsers (Chrome, Firefox, Safari, Edge) and should be disabled due to known vulnerabilities (including BEAST and POODLE attacks). SSL 2.0 and SSL 3.0 are completely insecure and should never be enabled on any modern server. Our SSL Checker shows exactly which protocol versions your server supports.

An A+ SSL grade requires everything needed for an A grade plus a fully functional HSTS policy. Common reasons for not achieving A+ include: HSTS not configured � the most common reason; HSTS max-age too short � must be at least 180 days (recommended: 1 year or 31536000 seconds); HSTS not applied to all subdomains � missing the includeSubDomains directive; Certificate chain issues � incomplete or incorrect intermediate certificate configuration; Weak cipher suites enabled � supporting outdated ciphers like RC4, 3DES, or CBC-mode ciphers; Insecure protocol versions enabled � TLS 1.0 or 1.1 still active; Key exchange weaknesses � using 1024-bit DH parameters or weak RSA keys; Missing certificate transparency information. Check our detailed results to identify specific areas for improvement.

Yes, this SSL Checker tool is completely free to use with no limitations, no registration, no API keys, and no usage caps. You can check as many domains as you need, as often as you like. There are no hidden fees, no premium tiers, and no data collection. The tool uses the free mate.tools SSL API for certificate analysis. If you find this tool valuable, consider sharing it with others who might benefit from it.
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