An SSL certificate encrypts data between a website and its visitors' browsers. An expired or misconfigured certificate drives users away, hurts search rankings, and exposes the site to attacks. The SSL checker at sites.reviews lets you verify in seconds that a certificate is valid, issued by a trusted authority, and covers the right domains.
How to use the tool
Enter the domain name in the input field — without https:// and without a trailing slash. For example: example.com. Click "Check". The tool connects to the server on port 443, retrieves the certificate, and parses its fields. Results appear within 3–5 seconds. No registration or plugin installation required.
Run a check in these situations:
- before launching a new site or subdomain;
- after renewing or reissuing a certificate with your hosting provider;
- when a browser or search engine reports a security error;
- periodically — to avoid missing an expiration date.
What the results show
The report covers all key certificate parameters:
- Issuer (CA). Who issued the certificate: Let's Encrypt, Sectigo, DigiCert, and others. Well-known certificate authorities receive higher trust from browsers.
- Validity period. The "Valid from" and "Valid to" dates — confirm the certificate is already active and has not yet expired.
- Days until expiry. The number of days remaining before the certificate expires. Best practice is to renew at least 30 days in advance.
- SAN domains. The full list of domains and subdomains covered by the certificate (Subject Alternative Names). Make sure your domain appears in this list.
Frequently asked questions
What does an expired certificate mean?
Once the expiry date has passed, the certificate is considered invalid. Browsers display a "Your connection is not private" warning, and most visitors will immediately leave the page. Search engines demote such sites in rankings. The fix is to reissue the certificate immediately through your hosting provider or via Let's Encrypt.
What is the difference between DV and EV?
DV (Domain Validation) only confirms ownership of the domain and is issued automatically within minutes. OV (Organization Validation) requires verification of company details. EV (Extended Validation) is the strictest level: the certificate authority manually verifies the legal entity. For most websites, a DV certificate is sufficient.
Why does the browser say "Not secure" even though I have a certificate?
The most common reason is mixed content: the page is loaded over HTTPS, but some resources — images, scripts, or fonts — are referenced via HTTP. Other causes include: the certificate does not cover the subdomain in use, the trust chain is broken due to a missing intermediate certificate, or the certificate has already expired.
Do I need to check subdomains separately?
Yes, if you have multiple subdomains. A wildcard certificate (e.g. *.example.com) covers only one level of nesting. A third-level subdomain such as api.shop.example.com is not covered. Check each subdomain individually or review the SAN list in the results.
Want to learn more? Read the full SSL certificate guide.