SSL Certificate Checker
Check SSL certificate validity, expiry date, issuer, and covered domains for any website.
Last year I was auditing a mid-sized e-commerce client’s domain migration when I noticed something odd. Their primary domain looked fine in a browser, but two subdomains api.client-domain.com and cdn.client-domain.com were quietly serving the wrong certificate for their SAN entries. Nobody on the client’s side had caught it because a browser only shows you the certificate for the exact address you’re visiting, not the ones sitting behind it. It took under 20 seconds with a certificate checker to confirm the mismatch, and about four hours to get it corrected before it reached their support queue. That’s the gap this kind of tool is built to close.
What This SSL Certificate Checker Does
This is a free, online SSL certificate checker that connects to a website over its secure port and reads back exactly what the server is presenting: the certificate chain, the issuing certificate authority, the validity window, the Subject Alternative Names (SANs) covered, and the TLS protocol version in use. It’s the same handshake your browser performs when it loads a page, we just surface the raw details instead of hiding them behind a padlock icon.
You don’t need to install anything or create an account. Enter a domain, and the tool returns a plain-language readout you can act on immediately.
Where This Website SSL Certificate Checker Gets Used
- Pre-migration checks: confirming a new server or CDN is presenting a valid certificate before DNS cutover
- Subdomain and SAN audits: catching certificates that don’t actually cover every subdomain they’re supposed to
- Expiry tracking: spot-checking validity dates across a portfolio of client sites ahead of renewal deadlines
- Debugging browser warnings: figuring out whether a “Not Secure” message is caused by an expired cert, a broken chain, or a mismatched hostname
- Post-deployment QA: verifying SSL is installed correctly before handing a site back after a hosting or CDN change
How to Use the Online SSL Certificate Checker
- Enter the domain or URL you want to check no need to include “https://”.
- Run the check. The tool connects to the server and reads its certificate directly.
- Review the results: issuer, validity dates, SAN list, and chain status.
- If something’s flagged expired, self-signed, or mismatched take it to your host or CDN provider with the exact detail in hand.
Features
- Checks any publicly reachable domain or subdomain, no login required
- Displays the full certificate chain, not just the leaf certificate
- Lists all SAN entries covered by the certificate
- Shows issuer, issue date, and expiry date at a glance
- Flags expired, self-signed, or hostname-mismatched certificates
- Works on non-standard ports, not just 443
Where This Tool Has Limits
This checker only reaches certificates on publicly accessible ports it can’t see behind a VPN, firewall, or authentication wall. It’s a point-in-time check, not continuous monitoring; for expiry tracking across a large client portfolio, pair it with a scheduled monitoring system. A clean result also doesn’t guarantee every device trusts the chain equally older operating systems with outdated root stores can still reject a certificate that resolves fine server-side. And this tool verifies the certificate itself; it doesn’t audit cipher strength or full TLS configuration, which is a separate kind of review.
Why We Built This
Our technical SEO team runs a certificate check as a standard step in every migration and pre-launch checklist we use internally a broken chain or an expired cert can undo weeks of technical work in a single afternoon. We built this tool to that same standard: fast, accurate, and readable without needing a networking background.
Frequently Asked Questions
Is this SSL certificate checker actually free?
Yes. There’s no signup, no trial period, and no limit tied to an account check as many domains as you need.
Does it work on any website, or only ones I manage?
Any publicly accessible domain. Certificates are part of the public handshake a server presents to any visitor, so you can check a client’s site, a competitor, or your own.
How is this different from checking the padlock icon in my browser?
Your browser only shows you the certificate for the exact page you’re on, and it summarizes rather than lists the full chain. This tool shows every certificate in the chain, all SAN entries, and the issuer detail your browser tucks away behind a click.
Do you log or store the domains I check?
No. Checks are run against the domain in real time and aren’t stored or used for anything beyond returning your result.
Run your first check now enter a domain above and see exactly what its SSL certificate is telling browsers and crawlers.