SSL Checker

All tools

Check the SSL/TLS certificate of any website — valid or not, expiry countdown, issuer, protocol, SANs and chain — in seconds. Free.

Enter a hostname to inspect its TLS certificate server-side. Results are cached for a few minutes.

Issued to
—
Issued by
—
Valid from
—
Valid until
—
Signature algorithm
—
Protocol
—

Covered domains (SANs)

Certificate chain

About SSL Checker

The SSL Checker connects to any hostname on port 443 and inspects its TLS certificate server-side. In seconds you get a clear valid-or-invalid verdict, an expiry countdown in days, the subject and issuing certificate authority, the validity window, the signature algorithm and the negotiated TLS protocol version.

It also lists every domain the certificate covers through its Subject Alternative Names (SANs) — essential when you need to confirm that a wildcard or multi-domain certificate really includes the subdomain you are deploying — and shows the certificate chain link by link, so you can spot a missing intermediate certificate.

Validity is verified properly: the tool performs a second handshake with full peer and hostname verification enabled, so a certificate that is merely present but untrusted, expired or issued for the wrong name is flagged as invalid. Use it to check SSL certificate expiry online before the browser warnings start.

How to use SSL Checker

  1. Enter the hostname you want to check, such as example.com — no https:// prefix needed.
  2. Click “Check certificate” and let the server complete the TLS handshake.
  3. Read the validity badge and the expiry countdown to see how many days remain.
  4. Review the issuer, validity dates, signature algorithm and protocol version.
  5. Open the SANs list to confirm every domain and subdomain the certificate covers.
  6. Inspect the certificate chain to verify the intermediates are served correctly.

Frequently asked questions

It runs a second TLS handshake with full verification enabled: the chain must be trusted, the hostname must match and the current date must fall inside the validity window. Only when all three pass is the certificate marked valid.

Subject Alternative Names list every hostname a certificate protects. If your subdomain is missing from the SANs, browsers show a name-mismatch warning even though the certificate itself is otherwise valid.

The most common cause is a missing intermediate certificate: the server sends only the leaf, so the chain cannot be verified. Check the chain section — if it is unusually short, install the full chain bundle on your server.

No. The checker connects to port 443 only, which covers standard HTTPS. For services running TLS on other ports, use a command-line client such as openssl s_client from your own machine.

Only the hostname you type. The TLS connection is made from our server, and results are cached for a few minutes. Hosts that resolve to private or internal addresses are refused.

Yes, completely free. Lookups are rate-limited per visitor, so occasional heavy use may ask you to wait a minute between checks.
Share this
Related Tools
HTTP Status Codes Look up every HTTP response status code (1xx–5xx) in a searchable, filterable directory — then open any code for what it means, when to use it, whether it is cacheable and the RFC that defines it. In your browser, free. Free
HTTP Methods A scannable reference for every HTTP request method — GET, POST, PUT, PATCH, DELETE and the rest, plus WebDAV — showing at a glance whether each one is safe, idempotent and cacheable, if it takes a body, and a typical example. In your browser, free. Free
HTTP Headers Reference Look up common HTTP request and response headers in a searchable directory — filter by direction and category, read a one-line description and a realistic example, and copy any header name with one click. In your browser, free. Free
DNS Record Types Browse every common DNS record type — A, AAAA, CNAME, MX, TXT, NS, SOA, PTR, SRV, CAA, DNSKEY, DS, TLSA and more — with its purpose, a copyable zone-file example and a category. Search and filter instantly, in your browser, free. Free
TCP/UDP Port Numbers Look up well-known and commonly-used network ports in a searchable table — FTP, SSH, HTTP, HTTPS, MySQL, Postgres, RDP, Redis, MongoDB and 120+ more, each with its transport protocol, service, description and category. Search by port number or service name and copy values instantly. In your browser, free. Free
Subnet / CIDR Calculator Calculate IPv4 subnets from CIDR or mask: network, broadcast, host range, wildcard and more. Free
Popular searches
ssl checker ssl certificate checker check ssl expiry tls certificate check ssl expiration date checker certificate checker online https checker ssl test free
Need help?
Found an issue with this tool? Let our team know.
Report an issue

Add this free tool to your own website — copy and paste the code below.