SSL Certificate Checker
Inspect the TLS certificate of any site - expiry, issuer, SANs and chain
100% free. This tool needs our server to do the work, so what you submit is sent there, processed and then discarded - it is never stored.
About this tool
Inspect a website's TLS/SSL certificate - checking its expiry date, issuer, Subject Alternative Names (SANs), and the full certificate chain. Useful for verifying a certificate is valid and won't expire soon, or diagnosing HTTPS trust issues on your own or another site.
Diagnose a slow or unreachable website
Work outwards: is the host answering, is the page slow, and is the certificate still valid.
- 1Ping the hostLatency, jitter and packet loss.Open
- 2Run a speed testReal browser-rendered performance audit.Open
- 3Check the certificateAn expired one blocks every visitor.You are here
- 4Inspect DNSConfirm the records point where you expect.Open
How to use this tool
- Enter domain/hostQuery live certificate presented by the server over HTTPS.
- Inspect certificate detailsReview issuer, validity period, SAN list, and signature chain.
- Check expiry and coverageConfirm all required hostnames are covered and not near expiration.
- Fix cert/deployment issuesRenew, reissue, or complete chain configuration on server/CDN.
Common SSL certificate problems
An expired certificate shows a full-page browser warning, which stops most visitors. A name mismatch means the certificate does not list the domain being visited - often the www or non-www version is missing from the SANs. An incomplete chain means the server is not sending the intermediate certificate, so some devices cannot verify it.
Use automatic renewal where you can, and set a reminder at least two weeks before the expiry date for any certificate renewed by hand.
Key features
- Prevents production outages caused by expired certificates.
- Diagnoses trust errors from incomplete chain configuration.
- Validates SAN coverage for multi-subdomain deployments.
- Supports proactive HTTPS monitoring and incident prevention.
Common uses
- Checking cert health before major traffic campaigns.
- Debugging browser “connection not private” warnings.
- Auditing wildcard and SAN certificate deployments.
- Validating post-renewal certificate installation success.
Tips for better results
- Renew certificates before expiry window gets tight.
- Include both root and intermediate chain correctly on server.
- Verify all public subdomains in SAN list after reissue.
- Retest from CDN edge hostnames if proxy is involved.
Mistakes to avoid
- Renewing certificate but not deploying updated chain.
- Assuming wildcard cert covers every needed hostname pattern.
- Ignoring staging cert warnings until production incident occurs.
- Checking only apex domain while `www` remains misconfigured.
Frequently asked questions
Browsers will show visitors a security warning and typically block easy access to the site, since an expired certificate can no longer be trusted to verify the site's identity - this is why monitoring expiry dates matters, especially for production sites.
Additional domain names covered by the same certificate - for example, a certificate might cover both "example.com" and "www.example.com" as SANs, so both work correctly under HTTPS with one certificate.
It shows whether the certificate is properly linked back to a trusted root certificate authority through any intermediate certificates - a broken or incomplete chain can cause trust errors in some browsers/devices even if the certificate itself is technically valid.
Use automatic renewal - Let's Encrypt certificates last 90 days and are designed to renew automatically - and set a monitoring alert a few weeks before expiry in case renewal fails.
Usually a missing intermediate certificate: some browsers fetch it themselves while others fail. Install the full chain on your server so every client can verify the certificate.
Not for SEO - Google treats any valid HTTPS certificate the same. Domain-validated certificates are as secure in transit as organisation-validated ones; the difference is how much the issuer checked the owner.