Free SSL Certificate Checker
Check a public website in seconds. See whether visitors may hit a security warning, when the certificate expires, and what to do next.
Certificate check result
Check a public website in seconds. See whether visitors may hit a security warning, when the certificate expires, and what to do next.
Run a check to see the safety conclusion, expiry timing, domain coverage, and next step.
- Whether visitors may see a warning
- Expiry date and remaining time
- A plain next step, including email reminders
Use the same public check from curl or scripts. Register when you want continuous monitoring and email reminders.
curl 'https://certmonitor.xyz/api/v1/check?target=https%3A%2F%2Fgoogle.com'What we check
Cert Monitor checks the public HTTPS endpoint your customers can reach. The result focuses on whether the certificate is valid, when it expires, whether it covers the requested host, and which issuer signed it.
- Public domain or HTTPS URL reachability
- Certificate expiry date and days remaining
- Hostname coverage for the checked domain
- Issuer and customer-facing risk summary
How it works
The check runs from Cert Monitor servers on the public internet. We default to port 443, and you can enter a public custom TLS port when that is how customers visit the site.
- No account is needed for a one-time public check
- Private, local, reserved, and metadata addresses are blocked
- Register only when you want continuous monitoring and email reminders
Common errors
A failed check usually means we cannot confirm the customer-facing certificate from the public internet. Common causes include DNS issues, closed public ports, an HTTPS service that is not responding, or firewall/CDN rules that block external checks.
Why reminders matter
Shorter certificate lifetimes and automated renewals reduce manual work, but they also make missed renewal jobs more visible. Continuous monitoring gives small teams an email reminder before visitors see browser warnings.
API and curl usage
The same public check is available at /api/v1/check for curl or script usage. Registration is for continuous monitoring and email reminders, not for unlocking a higher check quota.