SSL Certificate Checker

What this SSL certificate checker does

This free SSL checker connects to a domain over HTTPS, reads the certificate the server presents, and shows you the key facts in one small table: who issued it, when it became valid, when it expires, how long the validity period is, which signature algorithm was used, and how many days are left before it expires. You do not need to install OpenSSL or open your browser's certificate viewer.

It is built for website owners, developers, sysadmins, agencies that look after many client sites, and anyone who wants a quick answer to "when does this certificate expire?" before a renewal deadline turns into a browser warning.

Modern websites actually use TLS, the successor to SSL, but the name "SSL certificate" stuck, so we use both terms here.

How to use the SSL checker

1. Type a domain name into the Domain field, for example example.com or www.example.com. You can paste a full URL; the protocol and path are ignored and only the host name is checked.
2. Click Check SSL.
3. Wait a moment while the server connects to the domain and reads its certificate.
4. Review the results table. If something looks wrong, check the other host names you use (with and without www, subdomains such as shop. or api.), because each one can serve a different certificate.

How to read the results

• Issuer – the name of the certificate authority (CA) certificate that signed this certificate. This is often an intermediate CA with a short name rather than the brand name of the CA company. If the issuer is the same as your own domain name, the certificate is probably self-signed.
• Valid from and Valid until – the start and end of the certificate's validity window, shown as day/month/year. Browsers reject the certificate outside this window.
• Validity period – the total lifetime of the certificate. When the certificate has already expired, this row tells you so instead.
• Signature algorithm – how the CA signed the certificate, for example RSA-SHA256 or ecdsa-with-SHA256. Both are current and widely supported. A certificate signed with SHA-1 or MD5 is obsolete and will not be trusted by modern browsers.
• Days left – the number of days until expiry. A negative number means the certificate has already expired by that many days.

Example

Suppose you check a site and see a validity period of about three months and 20 days left. That pattern is typical of a free, automatically renewed certificate. If automatic renewal is working, you should see a fresh certificate with a new "Valid from" date well before the days-left counter reaches zero. If the number keeps dropping across several checks, your renewal job may be broken.

Common use cases

• Confirming that a certificate renewal actually reached the live server, not just the certificate store.
• Auditing a list of client or company domains before a deadline.
• Checking a new subdomain after setting up a CDN, load balancer or hosting move.
• Investigating a "Your connection is not private" or "certificate expired" report from a visitor.
• Comparing certificates across environments, such as staging and production.

Why expiry dates matter more every year

Certificate lifetimes are getting shorter. Under the CA/Browser Forum's Baseline Requirements (Ballot SC-081), the maximum validity of a publicly trusted TLS certificate is 200 days for certificates issued from 15 March 2026, dropping to 100 days from 15 March 2027 and to 47 days from 15 March 2029. Shorter lifetimes mean more renewals, so automated renewal (for example with the ACME protocol) and regular expiry checks are no longer optional for most sites.

Tips and common mistakes

• Check every host name. example.com and www.example.com can be served by different servers or certificates. One can be fine while the other has expired.
• Know what this tool does not check. It reports the dates, issuer and algorithm of the certificate the server sends. It does not validate the full trust chain, and it does not confirm that the certificate's names match the domain. A self-signed certificate or a certificate for the wrong host can still show normal-looking dates here, so if browsers show a warning, check the certificate in the browser as well.
• Do not wait for the last day. Plan renewals well ahead of expiry so you have time to fix DNS, validation or deployment problems.
• Renewed but still old? If you renewed but the old dates still appear, the web server may need a reload, or a CDN or load balancer in front of it may still hold the old certificate.

Frequently asked questions

Is SSL the same as TLS?

SSL is the older protocol family. It has been replaced by TLS, and current browsers support only TLS. People still say "SSL certificate" out of habit, but the certificate is the same X.509 certificate used for TLS.

What happens when an SSL certificate expires?

Browsers show a full-page security warning and many visitors will leave. API clients, apps and payment integrations that connect to the site may fail completely until a valid certificate is installed.

Why does the issuer show a short code instead of a company name?

The issuer field shows the common name of the CA certificate that signed yours, which is usually an intermediate certificate. Many CAs give intermediates short names, so the code you see is normal.

Does this tool tell me if my certificate is trusted?

No. It reads dates, issuer and algorithm. It does not verify the chain of trust or that the host name matches. Use it as a quick expiry and details check, not as a full security audit.

Can I check a subdomain or a site that is not mine?

Yes. Certificates are public by design: any HTTPS client receives the certificate when it connects. You can check any publicly reachable host name.

Why is my certificate valid for only about 90 days?

Several certificate authorities, including popular free ones, issue short-lived certificates and expect you to renew them automatically. Short lifetimes limit the damage if a private key is ever exposed.

Related tools

• Ping IP – check whether a host responds and how long round trips take.
• Unix Timestamp Converter – convert certificate or log timestamps between epoch time and readable dates.
• Subnet Calculator – work out network ranges when you configure servers and firewalls.
• Robots.txt Generator – finish the technical setup of a new site.