SSL Checker

Check SSL certificate: dates, issuer, chain and mixed content.

What Is SSL/TLS?

SSL (Secure Sockets Layer) — and its successor TLS (Transport Layer Security) — are encryption protocols that ensure communication between a visitor's browser and the web server remains private and unaltered. When a site uses HTTPS, it means a valid SSL/TLS certificate is installed.

Why Is SSL Important?

Data Security

Without SSL, data exchanged between the user and the server (passwords, credit cards, personal information) can be intercepted by third parties in man-in-the-middle attacks.

SEO and Google Ranking

Google has used HTTPS as a ranking factor since 2014. Sites without SSL are demoted in search results.

Browser Warnings

Modern browsers (Chrome, Firefox, Safari) display a "Not Secure" warning on sites without HTTPS, discouraging visitors from proceeding.

E-commerce Requirement

For sites that accept payments, SSL is a mandatory requirement for PCI-DSS compliance.

What Does the SSL Checker Verify?

Issuer and Certificate Chain

Which Certificate Authority (CA) issued the certificate and whether the trust chain (certificate chain) is complete. An incomplete chain can cause errors in some browsers.

Expiry Date

When the certificate expires and how many days remain. An expired certificate makes the site inaccessible to most users.

Mixed Content

If the page loads resources (images, scripts, CSS) over HTTP instead of HTTPS, it appears to browsers as "mixed content" and may be blocked.

What Is Mixed Content and How to Fix It?

Mixed content occurs when an HTTPS page loads resources over HTTP. To fix it: find the HTTP URLs in your code (images, scripts, iframes) and change them to HTTPS, or use relative URLs. In WordPress, the "Really Simple SSL" plugin automates the process.

Frequently Asked Questions

How far in advance should I renew my SSL certificate?

Renewal is recommended at least 30 days before expiry. If you use Let's Encrypt with auto-renewal, the certificate renews automatically 30 days before it expires. For paid certificates, the provider usually sends a reminder email.

What is an intermediate certificate?

Certificate Authorities do not sign site certificates directly with their root certificate — they use an intermediate certificate. If the server does not send the intermediate, some clients cannot verify the trust chain, causing SSL errors.

Does the SSL Checker accept full URLs?

Yes, you can enter either a domain (e.g. example.com) or a full URL (e.g. https://example.com). The tool automatically extracts the hostname and checks the certificate on port 443.

What is the difference between Let's Encrypt and a paid SSL certificate?

Technically there is no difference in security — both encrypt communication equally effectively. Paid certificates (OV, EV) offer additional verification of the company's identity, which is useful for e-commerce and financial institutions.

📖 Read the full guide: How to Check an SSL Certificate →