SSL Certificate Checker
Inspect a website's SSL/TLS certificate: issuer, subject, valid dates, days remaining, the TLS protocol and whether the chain is trusted. A quick way to catch certificates before they expire. Runs server-side; nothing is stored.
- 100% free
- Secure
Why use SSL Certificate Checker?
SSL Certificate Checker performs a fast, secure server-side lookup and presents the results in a clear, readable format.
- Fast server-side lookup — we don't store your queries.
- Completely free, with no account, no watermarks and no usage limits.
- Handles Input: domain (port 443); Output: subject, issuer, validity, SAN, protocol.
- Enter a domain.
- Works on any device — desktop, tablet and phone — and is fully keyboard accessible.
What it can do — and its limits
- Checks a site's SSL/TLS certificate: issuer, validity dates, days until expiry and chain trust.
- Runs as a secure server-side request (a browser can't inspect another site's certificate directly).
How to use SSL Certificate Checker
- Enter a domain.
- Click Check.
- See issuer, validity and days remaining.
- Note the expiry to renew in time.
Examples
- Confirming a certificate isn't about to expire.
- Checking who issued a site's certificate.
Worked example
Input
example.com
Output
Issued by a trusted CA, valid until 10 Jan 2027 (chain OK).
Supported formats & limits
- Input: domain (port 443)
- Output: subject, issuer, validity, SAN, protocol
Limitations
- Checks the certificate served on port 443 at lookup time.
- Untrusted or self-signed chains are reported but still shown.
Common problems & fixes
'Hostname mismatch'.
The certificate doesn't cover the exact hostname you entered — check for www vs apex or a wrong SAN.
'Expired' or 'self-signed'.
Renew the certificate, or install one from a trusted CA such as Let's Encrypt.
Sources & references
Last verified August 2026.
Frequently asked questions
What does 'trusted' mean?
It indicates the certificate chain validates against standard certificate authorities.
Why a server-side check?
Reading another site's TLS certificate requires a direct TLS connection browsers don't allow.
Are lookups stored?
No.