SSL Certificate Checker Tool Online
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Check any website's SSL/TLS certificate instantly. See the issuer, expiry date, protocol version, cipher suite, and whether HSTS is enabled.
Enter a domain to check its SSL certificate:
How the SSL Certificate Checker Works
This tool connects directly to a website's server and inspects its SSL/TLS certificate. Here's the process:
- Enter a domain — type or paste any website address. The tool extracts the hostname automatically.
- TLS handshake — the checker opens a secure connection on port 443 and performs a full TLS handshake to retrieve the server's certificate.
- Certificate analysis — it reads the certificate details: issuer, subject, validity dates, serial number, SANs, key type, cipher suite, and TLS protocol version.
- HSTS check — simultaneously, it makes an HTTP request to check whether the
Strict-Transport-Securityheader is present.
Why SSL Certificates Matter for Your Website
SSL certificates are no longer optional — they're a baseline expectation for every website. Here's why they matter:
- Encryption — SSL encrypts data between the browser and server. Without it, passwords, form submissions, and payment details are sent in plain text.
- Trust — browsers display a padlock for HTTPS sites and show "Not Secure" warnings for HTTP. A missing or expired certificate erodes visitor trust instantly.
- SEO ranking signal — Google has used HTTPS as a ranking factor since 2014. A valid SSL certificate is part of your site's SEO foundation.
- GEO and AI search — AI search engines like ChatGPT Search and Perplexity also consider HTTPS when evaluating source trustworthiness. A properly configured SSL supports your GEO strategy.
- Compliance — GDPR, PCI-DSS, and other regulations require encrypted connections for handling personal or payment data.
What to Check in Your SSL Results
When you run a scan, focus on these key indicators:
- Days remaining — if your certificate expires in less than 30 days, renew it now. Expired certificates trigger browser warnings that effectively take your site offline.
- Issuer — should be a recognized Certificate Authority (Let's Encrypt, DigiCert, Sectigo, Cloudflare, etc.). Self-signed certificates are not trusted by browsers.
- TLS protocol — TLS 1.2 minimum, TLS 1.3 preferred. Anything older is deprecated and insecure.
- SANs coverage — make sure all your domains and subdomains (www, mail, api) are listed in the Subject Alternative Names.
- HSTS enabled — if missing, browsers can still access your site via HTTP on the first visit. Enable HSTS to force HTTPS from the start.
For a complete site health check, pair this with the DNS Lookup Tool and Robots.txt Tester to verify your domain configuration, SSL, and crawler access in one pass. Also check your security headers — SSL alone doesn't protect against clickjacking or MIME-type attacks, which headers address. For email security, the Email Deliverability Checker audits SPF, DKIM, and DMARC on the same domain.
SSL Certificate Checker: FAQ
What is an SSL certificate?
An SSL (Secure Sockets Layer) certificate is a digital credential that encrypts the connection between a visitor's browser and a website's server. When a site has a valid SSL certificate, the browser shows HTTPS and a padlock icon. Modern certificates actually use TLS (Transport Layer Security), the successor to SSL, but the term SSL is still widely used.
What does this SSL certificate checker do?
This tool connects to a website's server on port 443 (HTTPS) and retrieves the full SSL/TLS certificate details. It shows the issuer, expiry date, days remaining, subject alternative names (SANs), cipher suite, protocol version, key type, and whether HSTS is enabled. It also flags expired, self-signed, or untrusted certificates.
Why should I check my SSL certificate?
Expired or misconfigured SSL certificates cause browser warnings that scare away visitors and hurt SEO rankings. Google has used HTTPS as a ranking signal since 2014. Regular SSL checks help you catch expiring certificates before they cause downtime, verify correct installation after renewals, and confirm that your encryption is up to date.
What does "days remaining" mean?
It shows how many days are left before your SSL certificate expires. Most certificates are issued for 90 days (Let's Encrypt) or 1 year (commercial CAs). When the counter hits zero, browsers will display security warnings and your site effectively goes offline for trust purposes. We recommend renewing at least 30 days before expiry.
What is HSTS and why does it matter?
HSTS (HTTP Strict Transport Security) is a header that tells browsers to always use HTTPS when connecting to your site, even if someone types http://. Without HSTS, a visitor's first request might go over unencrypted HTTP before being redirected. HSTS eliminates that window of vulnerability. This tool checks whether HSTS is enabled on your domain.
What are Subject Alternative Names (SANs)?
SANs are additional domain names covered by a single SSL certificate. For example, a certificate for example.com might also include www.example.com, api.example.com, and mail.example.com as SANs. This tool lists all SANs so you can verify that all your domains and subdomains are covered.
What does "self-signed certificate" mean?
A self-signed certificate is one that was not issued by a trusted Certificate Authority (CA). Browsers do not trust self-signed certificates and will show security warnings. They are fine for local development but should never be used on production websites. If this tool flags a self-signed certificate, you need to install a proper one from a CA like Let's Encrypt, DigiCert, or Sectigo.
Which TLS protocol version should my site use?
TLS 1.2 or TLS 1.3. TLS 1.3 is the latest and fastest — it reduces handshake latency and removes older cipher suites. TLS 1.0 and 1.1 are deprecated and no longer supported by modern browsers. If this tool shows your site using anything older than TLS 1.2, you should update your server configuration.
Is this SSL checker free to use?
Yes. This SSL certificate checker is completely free with no signup, no limits, and no ads. It is built for website owners, developers, and agencies who need a fast way to verify SSL certificates.
Does this tool store the domains I check?
No. The tool only performs the SSL check and returns the result. We do not store domains, certificates, or any personal data through the checking process.
Need Help Securing Your Website?
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