SSL/TLS certificate checker
Certificate validity, expiry date, issuer, TLS version, TLS 1.0/1.1 support and HTTPS redirect: a free diagnosis in seconds.
Passive scan: we only read public information (DNS, home page, certificate). No port scanning, no intrusion attempts. Active testing requires written authorization (Criminal Code, s. 342.1).
What the tool checks
- Certificate validity: chain of trust, domain name, expiry.
- Negotiated TLS version: ideally TLS 1.3, TLS 1.2 at minimum.
- Outdated versions: does the server still accept TLS 1.0 or 1.1?
- Redirect: does http:// send visitors to https://?
Avoiding expired certificates
An expired certificate shows a security warning to every visitor. Automate renewal (ACME, Let’s Encrypt or your host’s tools) and add a calendar alert 30 days before expiry for manually renewed certificates.
Frequently asked questions
How do I know when my SSL certificate expires?+
Enter your domain: the tool connects over HTTPS, reads the certificate presented and shows the issuer, the negotiated TLS version and the number of days before expiry.
Why are TLS 1.0 and 1.1 a problem?+
These versions are formally deprecated (RFC 8996) and no longer offer adequate protection. Your server or CDN should accept only TLS 1.2 and 1.3.
SSL or TLS: what’s the difference?+
SSL is the old name. Modern HTTPS connections use TLS; “SSL certificate” simply stuck in everyday language.