SSL Checker Online — Verify SSL Certificate Status and Expiry Free
An SSL checker online inspects a website's SSL/TLS certificate and returns its key details — expiry date, issuer, subject alternative names, certificate chain, and protocol version. Use it to verify that HTTPS is correctly configured, catch certificates approaching expiry before they cause browser warnings, and confirm that your certificate covers all the domains you need.
What Is an SSL Certificate?
An SSL certificate (more accurately called a TLS certificate today — SSL is deprecated) is a digital document issued by a Certificate Authority (CA) that proves a server's identity and enables encrypted HTTPS connections. When your browser connects to a website over HTTPS, the server presents its certificate; the browser verifies it was issued by a trusted CA, that it covers the domain you requested, and that it has not expired. If all checks pass, the browser establishes an encrypted connection and displays the padlock icon.
Certificates have a fixed validity period — currently capped at 398 days for publicly trusted certificates. When a certificate expires, browsers show a full-screen warning that blocks most users from reaching the site. An expired certificate is one of the most avoidable causes of website downtime.
What the SSL Checker Verifies
| Check | What It Means | Why It Matters |
|---|---|---|
| Certificate expiry date | When the certificate stops being valid | Expired certs trigger browser warnings; renew at least 30 days before expiry |
| Issuing CA | Which Certificate Authority signed the cert | Confirms the cert came from a trusted source (Let's Encrypt, DigiCert, Sectigo, etc.) |
| Domain coverage (SANs) | Which domain names the cert is valid for | A cert for example.com does not cover www.example.com unless both are listed as SANs |
| Certificate chain | The chain from your cert to a root CA | An incomplete chain causes "untrusted" warnings in some browsers and clients |
| TLS protocol version | Which TLS versions the server accepts | TLS 1.0 and 1.1 are deprecated; servers should use TLS 1.2 or 1.3 only |
| HTTPS redirect | Whether HTTP requests redirect to HTTPS | HTTP traffic is unencrypted; all requests should redirect to HTTPS |
How to Use the SSL Checker
- Enter the domain. Type the hostname you want to check — for example,
example.comorwww.example.com. Do not include the protocol (https://). - Run the check. Click Check. The tool connects to the server, retrieves the certificate, and displays the results.
- Review the output. Check the expiry date, confirm the domains covered match what you expect, and verify the chain is complete.
Certificate Expiry — How to Stay Ahead
Set up monitoring and alerts
The best way to avoid certificate expiry incidents is automated monitoring. Many services — UptimeRobot, Datadog, Cloudflare, AWS Certificate Manager — can send alerts when a certificate is within 30, 14, or 7 days of expiry. Set alerts at 30 days and treat them as urgent.
Use Let's Encrypt with auto-renewal
Let's Encrypt issues free 90-day certificates with a Certbot client that renews automatically every 60 days. When configured correctly, you never need to manually renew. The 90-day validity period is intentional — it forces automation and limits the window of exposure if a certificate is compromised.
Managed certificates via hosting provider
Most major hosting platforms (Vercel, Netlify, AWS CloudFront, Cloudflare) provision and renew certificates automatically. If your site is behind one of these services, certificate management is handled for you — but it is still worth checking periodically that the certificate is valid and covers all your domains.
Common SSL Problems and What They Mean
Certificate name mismatch
The certificate covers example.com but the user is accessing www.example.com (or vice versa). Solution: reissue the certificate as a SAN certificate covering both domains, or configure a redirect so both point to the covered domain.
Incomplete certificate chain
The server is only sending the leaf certificate, not the intermediate CA certificates. Browsers can sometimes download intermediate certs automatically, but many clients (APIs, mobile apps, older browsers) cannot. Solution: configure your web server to send the full chain file (usually a combined fullchain.pem file provided by Let's Encrypt and most CAs).
Mixed content warnings
The page is served over HTTPS but contains resources (images, scripts, stylesheets) loaded over HTTP. Browsers block or warn about mixed content. Solution: update all resource URLs to use https:// or relative URLs, and check that your CMS or template does not hardcode HTTP asset paths.
Common Questions
What is the difference between SSL and TLS?
SSL (Secure Sockets Layer) was the original protocol; TLS (Transport Layer Security) is its successor and is what all modern HTTPS connections use. SSL 2.0 and 3.0 are long deprecated. The term "SSL certificate" persists colloquially even though the certificates are used with TLS. When someone says "SSL," they almost always mean TLS 1.2 or TLS 1.3 in practice.
Does my site need an SSL certificate for SEO?
Yes. Google has used HTTPS as a ranking signal since 2014. More importantly, browsers show "Not Secure" warnings for HTTP pages, which increases bounce rates. Any site collecting data — including analytics cookies — should use HTTPS. Free certificates from Let's Encrypt remove the cost barrier entirely.
Check Your SSL Certificate Now
Enter any domain and instantly see certificate expiry, issuer, covered domains, chain status, and TLS version — free, no signup.
Open SSL Checker