Free SSL Certificate Checker
Enter a domain to check SSL certificate expiry, confirm the SSL expiration date, inspect the issuer, and see whether the hostname and certificate chain are valid.
Check any public hostname
Check certificate expiry
Validate hostname coverage
Inspect trust signals
Plan SSL monitoring
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Create a free monitor to watch SSL expiration dates and receive SSL expiration email alerts before your sites break.
An SSL certificate proves that a website can create an encrypted HTTPS connection for a specific hostname. This free SSL checker gives a quick answer near the top of the page, then shows the certificate details that usually matter when you are investigating an outage, validating a renewal, or confirming that a domain is ready for production traffic.
What is an SSL certificate?
An SSL certificate, more accurately called a TLS certificate today, is a digital certificate used by a web server during the HTTPS handshake. It identifies the hostname, contains public key information, and is signed by a certificate authority or another trusted issuer. Browsers use it to decide whether they can establish an encrypted connection without warning the visitor.
A certificate does not prove that a business is trustworthy by itself. It proves that the server can present a certificate that matches the hostname and chains back to a trusted issuer. That distinction is important: SSL is a transport security control, not a full security audit.
What does this SSL checker show?
The checker connects to the public hostname and reports the certificate currently served by that endpoint. The result includes the status, issuer, validity window, expiration date, days remaining, hostname match, trusted chain status, TLS protocol, cipher details, and Subject Alternative Name entries when available.
- Use the expiration date to confirm whether renewal is urgent.
- Use the days remaining value to check SSL certificate expiry risk quickly.
- Use hostname match and SAN domains to verify wildcard and subdomain coverage.
- Use issuer and chain status to spot unexpected providers or trust problems.
How to check SSL certificate expiration
Enter a domain such as example.com, submit the check, and read the “Valid until” and “Days remaining” fields in the result. If the number of days remaining is low, plan the renewal before the deadline rather than waiting for a browser error. Many teams set a warning threshold around 30 days and a critical threshold around 7 days, but the right threshold depends on how certificates are issued and deployed.
If your website uses multiple hostnames, check each public hostname that users visit. A certificate can be valid for one name and invalid for another if the SAN list does not include the second hostname.
Common SSL certificate problems
- Expired certificates that make browsers show a privacy warning.
- Hostname mismatches, such as a certificate for www.example.com being served on app.example.com.
- Missing intermediate certificates that prevent some clients from building a trusted chain.
- Self-signed or privately issued certificates on public websites.
- Certificates that are valid but close enough to expiration that renewal should be handled soon.
These problems often appear after a hosting migration, CDN change, load balancer update, or incomplete certificate renewal. The website might work for some users and fail for others if different edge servers are serving different certificates.
What happens when an SSL certificate expires?
When a certificate expires, browsers and API clients can reject the HTTPS connection. Visitors may see a full-page security warning instead of the site. Automated integrations can fail with certificate validation errors. Search crawlers and uptime monitors may also mark the page as unhealthy if they cannot complete a trusted HTTPS request.
The business impact depends on the site, but the technical failure is simple: the certificate is outside its valid date range, so clients have no reason to trust it for a secure connection.
How to monitor SSL certificates automatically
Manual checks are useful during setup and troubleshooting. Automatic monitoring is better for production domains because expiration is time-based and easy to miss. Website Certs can monitor a domain and alert you when certificate health changes, including expiration risk and related HTTPS or DNS issues that may affect the same hostname.
After you run a check, use the monitoring button in the result card to start tracking the checked domain and receive SSL expiration email alerts. Anonymous visitors are sent to registration with the domain prefilled, while signed-in users go directly to the new domain monitor flow.
Read the monitoring guide to manage certificate expiration risk with inventories, alert windows, renewal verification, and ownership. For reminder-focused workflows, use the SSL expiration email alerts guide.
Related website checks
SSL is only one part of a healthy public website. You can also inspect the records that point traffic to a host with the DNS checker and test response status, redirects, and TLS request errors with the HTTPS checker. After TLS is working, use the Security Headers Checker to review HSTS, CSP, Referrer-Policy, and other browser security headers.
SSL certificate guides
FAQ section
What is an SSL checker?
An SSL checker inspects the certificate served by a public hostname and reports details such as expiration date, issuer, hostname coverage, and whether the certificate chain is trusted.
How do I check when my SSL certificate expires?
Enter the domain in the checker, submit the check, and read the valid until and days remaining fields in the result. Check each public hostname that users visit.
What happens if my SSL certificate expires?
When an SSL certificate expires, browsers and API clients can reject the HTTPS connection. Visitors may see a security warning instead of the website.
Can Website Certs monitor SSL certificates automatically?
Yes. Website Certs can monitor a domain and alert when SSL certificate health changes, including expiration risk and related HTTPS or DNS issues.