Free SSL Certificate Checker
Enter any domain below to inspect its SSL/TLS certificate. View the issuer, expiry date, protocol version, Subject Alternative Names and whether the certificate chain is trusted.
New to SSL/TLS? Read our SSL Certificate Monitoring guide for a full explanation.
What is an SSL certificate?
An SSL (Secure Sockets Layer) certificate, more accurately called a TLS (Transport Layer Security) certificate, is a digital credential that authenticates a website's identity and enables an encrypted connection between a web server and a browser. Without a valid certificate, browsers display security warnings that erode visitor trust and can hurt search engine rankings.
Why should you check SSL certificates regularly?
- Prevent Downtime: An expired certificate triggers browser warnings, blocking visitors and breaking API integrations.
- SEO Impact: Google uses HTTPS as a ranking signal. A broken certificate can cause indexing issues.
- Compliance: PCI-DSS, HIPAA, and SOC 2 require valid encryption for data in transit.
- Supply Chain Security: Verify that third-party services your systems depend on maintain valid certificates.
How this tool works
Our checker connects to your domain on port 443, reads the certificate the server presents and checks whether the chain it sends is trusted, saying why when it is not. For a certificate that is otherwise valid it also reads the revocation list its certificate authority publishes, and says if the certificate has been revoked; when that list cannot be read, the result says revocation was not checked. There is no software to install, it is free, and a result can come from our cache for up to an hour.
Common SSL certificate problems
- Expired certificate: The most common issue. Browsers display a full-page warning and most users will leave immediately. Set up automated monitoring or use an auto-renewing provider like Let's Encrypt or Cloudflare.
- Hostname mismatch: The certificate was issued for a different domain (e.g. www.example.com but not example.com). Check the Subject Alternative Names (SANs) to see which domains are covered.
- Self-signed certificate: The certificate was not issued by a publicly trusted CA. Browsers will block access. Replace it with a certificate from a trusted provider.
- Incomplete certificate chain: The server is not sending the intermediate CA certificates. Some browsers can fetch missing intermediates, but others (especially mobile) will show an error. Our article on TLS certificate chain errors covers each cause and its fix.
- Mixed content: Your page loads over HTTPS but includes resources (images, scripts) over HTTP. This triggers browser warnings and can break functionality.
- Weak protocol or cipher: Using TLS 1.0 or 1.1 (deprecated) or weak cipher suites. Modern best practice is TLS 1.2+ with strong ciphers only.
Need automated SSL monitoring?
This free tool checks a certificate once. But certificates expire, issuers change, and misconfigurations happen without warning. ShieldMarc runs daily automated checks across all your domains and alerts you before a cert expires or a chain breaks. One dashboard, every domain. Start a 30-day free trial with no card needed.
Want the full picture?
Our Security Grade scans SSL/TLS alongside DMARC, SPF, DNSSEC, registration, and expiry in one scan.
Frequently asked questions
How often should I check my SSL certificate?
At minimum, check monthly. Certificate lifetimes have been shrinking across the industry, so a cert that was fine last month can be close to expiry today. Automated monitoring keeps you ahead of it. Daily automated checks come with ShieldMarc's SSL monitoring.
What is the difference between SSL and TLS?
SSL (Secure Sockets Layer) is the predecessor to TLS (Transport Layer Security). SSL versions 1.0 through 3.0 are all deprecated and insecure. Modern "SSL certificates" actually use TLS 1.2 or 1.3. The term "SSL" persists in common usage, but TLS is the correct protocol name.
Do I need an SSL certificate if my site does not handle sensitive data?
Yes. Google uses HTTPS as a ranking signal, browsers mark HTTP sites as "Not Secure", and even static sites benefit from encryption to prevent content injection by ISPs or network operators. Free certificates from Let's Encrypt or Cloudflare make there no reason not to use HTTPS.
Does SSL affect my Security Grade?
Yes. A valid SSL certificate is one of the checks in the Security Grade. It is the certificate being valid (trusted chain, correct hostname, not expired) that counts. How many days remain before renewal does not change your grade: ShieldMarc's SSL monitoring tracks upcoming expiry separately and alerts you before the certificate lapses, rather than lowering your grade for an imminent renewal.