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SSL Checker
Verify SSL certificate, issuer, expiration, chain. Free HTTPS security check.
What is SSL Checker?
SSL Checker is a free online tool that verifies the SSL/TLS certificate of a website. You enter a URL (e.g., https://example.com), click Check SSL, and the tool connects to the server, retrieves the certificate, and displays details such as the common name (CN), subject alternative names (SANs), validity period (valid from and to), issuer, algorithm, expiration summary, and the certificate chain. It also shows the resolved IP address and server information. This helps you verify that a site has a valid SSL certificate, when it expires, and whether it is properly configured. Webmasters use it to monitor their own certificates. Security-conscious users use it to verify sites before entering sensitive data. Developers use it to debug SSL issues.
SSL/TLS certificates encrypt data between the browser and the server. A valid certificate from a trusted Certificate Authority (CA) ensures the connection is secure and the server identity is verified. Certificates have an expiration date; they must be renewed periodically. The SSL Checker fetches the certificate chain, parses it, and presents the information in a readable format. You can see the common name (the domain the certificate is issued for), SANs (additional domains covered), validity dates, issuer (CA), and algorithm. The tool also shows how long until expiration (e.g., "Expires in 45 days"). If the certificate is invalid, expired, or misconfigured, the tool will indicate issues.
The tool displays quick status cards: resolved IP, server type, issuer, and expiration. A detailed table shows certificate information. If a certificate chain is present (intermediate certificates), each certificate in the chain can be expanded to view its details. The tool works with any publicly accessible HTTPS URL. For HTTP (non-encrypted) URLs, the tool may show an error or no certificate. Use the Sample button to test with an example. The Reset button clears the form.
Who Benefits from This Tool
Webmasters and system administrators monitoring their own SSL certificates benefit. They can verify installation and expiration. DevOps and security teams use it for quick certificate checks. Developers debugging SSL or mixed content issues use it. Users verifying a site before entering credentials benefit. Anyone responsible for website security benefits. The tool is free and requires no account. For continuous monitoring, use a dedicated certificate monitoring service.
Key features
URL Input
Enter any HTTPS URL. The tool connects and retrieves the certificate.
Certificate Details
Common name, SANs, validity dates, issuer, algorithm. Full certificate information.
Certificate Chain
Shows the chain (root, intermediates, leaf). Expandable sections for each certificate.
Quick Status
Resolved IP, server, issuer, expiration at a glance. Card layout for quick reading.
Expiration Summary
How long until the certificate expires. Helps with renewal planning.
How to use
- Open the SSL Checker tool.
- Enter the full URL (e.g., https://example.com). Use HTTPS.
- Complete the captcha if required.
- Click Check SSL.
- Review the certificate details. Check validity and expiration.
- Expand the certificate chain if present to see intermediate certificates.
Common use cases
- Verifying your own site's SSL certificate is valid and correctly installed
- Checking certificate expiration before renewal
- Debugging SSL errors or mixed content issues
- Verifying a site before entering sensitive information
- Auditing certificate configuration (SANs, chain)
- Comparing certificates across environments (staging vs production)
- Ensuring all domains on a certificate are correct
- Security audits and compliance checks
Tips & best practices
Use HTTPS URLs. HTTP sites do not have an SSL certificate to check. Set calendar reminders for certificate renewal before expiration. Most certificates are valid for 90 days or less (Let's Encrypt) or up to 13 months. Ensure your certificate covers all domains (SANs) you use. A valid chain (root and intermediates) is important for browser trust. Test from different locations if you use a CDN or load balancer. Combine with other security tools for a full audit.
Limitations & notes
The tool checks from the server's perspective. Results may vary by location due to CDNs or load balancers. It does not simulate browser behavior (e.g., OCSP stapling). Internal or private URLs may not be accessible. The tool does not store results. Certificate details are fetched in real time. For expired or invalid certificates, the tool will show the current state; it may not connect if the certificate is severely misconfigured.
FAQs
What is SSL?
Why does my certificate show as invalid?
What are SANs?
How often should I renew?
Can I check HTTP sites?
Is the tool free?
Does it check the full chain?
Why does the server show as "N/A"?
Can I check internal URLs?
Is my URL stored?
SSL/TLS certificates are essential for web security. They encrypt data in transit, preventing eavesdropping and tampering. They authenticate the server, so users know they are connecting to the right site. Browsers display a padlock and "Secure" for valid HTTPS sites. Invalid or expired certificates trigger warnings. The SSL Checker helps you verify your certificate is correctly installed and not expired. It shows the full chain: the leaf certificate (your site), intermediate certificates, and the root. A complete chain is required for browser trust. If an intermediate is missing, some browsers may show warnings. The tool displays each certificate in the chain with expandable sections. Check that the common name and SANs match your domains. A certificate for example.com will not work for www.example.com unless www.example.com is in the SANs. Many certificates cover both with a single SAN entry. The tool shows you exactly what is configured. Use it before go-live to verify. Use it periodically to monitor expiration. Set reminders for renewal. Let's Encrypt certificates expire every 90 days; commercial certificates may last up to 13 months. Do not let them lapse.
Certificate transparency and modern CA practices have changed the landscape. Most CAs now issue certificates with short validity. Automation is common. The SSL Checker does not replace a certificate monitoring service. For critical production sites, use a service that alerts you before expiration. This tool is for manual checks, debugging, and quick verification. When you get an SSL error in the browser, use the tool to see what the server is presenting. When you change hosting or add a CDN, verify the certificate is correct. When you add a new domain to a certificate, confirm it appears in the SANs. The tool gives you visibility. The quick status cards (IP, server, issuer, expiration) provide a snapshot. The detailed table and chain provide depth. Use both. The tool is free and requires no account. It connects to your server from its location; results may vary if you use geo-distributed infrastructure. For most single-server or simple CDN setups, the results are accurate. Bookmark the tool for your next SSL check.
Security best practices include regular certificate audits. The SSL Checker supports that. Run it quarterly or before major changes. Verify that your certificate uses a strong algorithm (e.g., SHA-256, not SHA-1). Check that the chain is complete. Ensure all your domains are in the SANs. If you use a wildcard certificate, verify it covers the subdomains you need. The tool displays the algorithm in the certificate details. Modern certificates use RSA or ECDSA with SHA-256 or better. Older algorithms may be deprecated by browsers. The tool helps you stay current. For developers, the SSL Checker is useful when debugging HTTPS issues. Mixed content, certificate errors, and chain problems can be tricky. Seeing the actual certificate and chain helps diagnose. The tool is a complement to browser developer tools and command-line utilities like openssl. It provides a user-friendly view. No command line, no parsing. Just enter the URL and read the results. Free, fast, and effective.
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