SSL Certificate Checker
Enter a domain name to see whether its HTTPS certificate is valid and trusted, when it expires, who issued it and which TLS version the server negotiates.
What this checker shows
- Validity and trust: whether the certificate is within its dates, matches the domain and chains to a trusted authority.
- Expiry: the exact date and how many days remain.
- Issuer: which certificate authority issued it.
- TLS version: the protocol version the server negotiated, for example TLS 1.3.
- Names covered: the domains the certificate is valid for.
Why certificates expire
Certificates have short lifetimes on purpose, so a stolen or outdated one stops working. When a certificate expires, browsers show a full-page warning and many visitors leave. Free certificates, such as those from Let’s Encrypt, typically last about 90 days and are meant to renew automatically.
Common certificate problems
- Expired: renew the certificate and restart or reload the web server.
- Name mismatch: the certificate does not list the domain you visit, for example it covers
example.combut notwww.example.com. - Untrusted issuer or self-signed: browsers do not trust it. Use a certificate from a recognised authority.
- Incomplete chain: the server must send its intermediate certificate too.
- Old TLS only: servers should support TLS 1.2 or 1.3, not TLS 1.0 or 1.1.
About this tool
When you press the button, our server connects to the domain you enter on port 443 and reads its public certificate, the same information any browser receives. We only connect to public internet hosts, we don't store the results, and requests are rate limited to keep the service fair for everyone.
Frequently asked questions
How do I check when an SSL certificate expires?
Enter the domain in the checker above. It shows the expiry date and the number of days remaining.
What happens when an SSL certificate expires?
Browsers show a security warning and many visitors leave. Renew the certificate and reload the web server to fix it.
What is a certificate chain?
A chain links your certificate to a trusted root authority through one or more intermediate certificates. The server must send the intermediates, or some browsers will not trust the site.
Is the SSL checker safe to use?
Yes. It only reads the public certificate that every visitor's browser already receives, and it does not store the results.
Related tools and guides
- Internet speed test: measure your connection.
- What is my IP address?: see your public IP.
- DNS speed test: compare public DNS resolvers.
- All tools: every CHECKiOX tool in one place.