Enter a hostname to check SSL/TLS certificate validity and expiry. Free tool — no account required.
An expired certificate triggers browser warnings, erodes user trust, and can hurt SEO. Regularly verify your critical domains.
Monitor automatically. For expiry alerts, use our SSL monitoring (free plan up to 5 monitors).
The checker connects to the site on port 443 and reads the certificate it actually serves:
If the checker reports an invalid certificate, the cause is usually one of these:
Automatic renewal failed or was never set up. Renew the certificate, then find out why renewal did not run (cron job, DNS or firewall blocking the validation).
The certificate covers example.com but not www.example.com, or a subdomain. Reissue it with every name you use, or use a wildcard certificate.
The server sends the certificate without its intermediate certificate. Some browsers and most apps then reject it. Install the full chain file from your certificate authority.
Fine for internal testing, never trusted by browsers on a public site. Replace it with a certificate from a public authority — Let’s Encrypt is free.
The server only offers TLS 1.0 or 1.1. Enable TLS 1.2 and 1.3 in your web server or hosting settings.
Since 15 March 2026, public SSL certificates are valid for 200 days at most. The limit drops to 100 days in March 2027 and to 47 days in March 2029. Let’s Encrypt certificates already last only 90 days.
In practice, every site now renews its certificate several times a year, and each renewal is a chance for something to break. A one-off check is not enough: monitoring warns you before the expiry date if a renewal fails.
To go further, read our guide: what is an SSL certificate, who issues it and what happens when it expires.
Enter a public hostname. We open a TLS connection on port 443, read the peer certificate and return issuer, validity dates and days remaining.
No. For security we only accept hostnames (or public IPs) and block private or local addresses to prevent SSRF abuse.
No. The checker is a one-off lookup. For continuous alerts before expiry, use UptimeFlux SSL monitoring on the free or paid plans.
The checker shows the issuer (certificate authority) of the certificate actually served on port 443 — for example Let's Encrypt, Sectigo or DigiCert — along with the subject and expiry date.
UptimeFlux monitors your certificates 24/7 and warns you in time.
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