About SSL Certificate Checker
The CSR.plus SSL Certificate Checker is a free online SSL checker that connects to any host and reports the full certificate details your visitors actually receive. Check validity, issuer, expiry, signature algorithm, TLS versions, and the complete chain to confirm a site is configured correctly and securely.
Whether you are verifying your own deployment, auditing a vendor, or troubleshooting "not secure" browser warnings, an SSL check tells you whether the certificate on the wire matches your expectations. This checker performs a live TLS connection, so the results reflect exactly what a visitor’s browser sees — including certificate chain completeness and supported TLS protocol versions.
Why use
- Verify SSL certificate validity, issuer, and expiry for any domain
- Check the complete certificate chain as served to browsers
- Confirm supported TLS versions and the negotiated configuration
- Free, no signup, and private — domains are checked live in your session
How to use
- Enter the hostname you want to check (for example example.com).
- Optionally set a custom port if the service is not on 443.
- The checker performs a live TLS connection and reads the presented certificate.
- Review the subject, issuer, validity, chain, and TLS versions to confirm everything is correct.
Frequently asked questions
▸Does it read the real certificate?
Yes. It opens a live TLS connection, exactly like a browser, to read what is actually served.
▸Can it check a specific port?
Yes. You can target any port when the service is not on the default 443.
▸Will it show the full chain?
It reports the certificate served by the host; ensure the server sends intermediates to avoid trust gaps.
▸Why does my browser say "not secure" but the checker says valid?
Usually a missing intermediate certificate, an expiring certificate in cache, or mixed-content on the page. Check the chain output and re-test after clearing cache.