SSL Certificate Checker
Inspect any domain's SSL/TLS certificate — validity, expiration, issuer, and TLS version. No account required.
Check Your Domain
What To Look For
Reading Your Certificate Results
Five operational indicators that determine whether a certificate is configured correctly and meeting your requirements.
Expiration Date
Certificates should have at least 30 days remaining. Plan renewal before the 30-day mark. Many certificate authorities send renewal reminders, but these should not be the only safeguard — configure monitoring alerts.
Trusted Issuer
The certificate should be issued by a recognized Certificate Authority. Self-signed certificates or unknown CAs will not be trusted by browsers, email clients, or API consumers.
Domain Coverage
Verify the Subject Alternative Names include all domains and subdomains that need to be covered. Missing a domain means that specific subdomain will show a certificate error.
TLS Version
TLS 1.2 or TLS 1.3 should be in use. If TLS 1.0 or TLS 1.1 is shown, the server configuration needs updating — these versions are deprecated and may violate compliance requirements.
Certificate Chain
Intermediate certificates must be properly chained. A valid leaf certificate with a broken chain will cause trust errors in some clients even if the end certificate itself is legitimate.
Why SSL Matters Operationally
SSL Certificates Are Infrastructure, Not Just Security
Certificate management is an operational discipline — failures disrupt service, erode trust, and create compliance gaps.
Service Continuity
An expired certificate takes down HTTPS access immediately — no graceful degradation. Users see trust errors. API consumers fail. Automated processes break. In healthcare, legal, and financial environments this means operational stoppage, not just inconvenience.
Compliance Alignment
PCI-DSS, HIPAA, and SOC 2 all have technical requirements around encryption in transit. Expired certificates, legacy TLS versions, and self-signed certs create audit findings. Certificate posture is often one of the first items reviewed in technical security assessments.
Client and Partner Trust
Browser trust warnings damage credibility with clients, partners, and stakeholders. Even a brief lapse in certificate validity creates a documented incident that may need to be reported to clients in regulated industries.
Automation Compatibility
Modern integrations — APIs, webhooks, third-party platforms — verify SSL certificates programmatically. A broken or expired certificate silently breaks integrations that your team may not notice immediately.
FAQ
Common Questions
What does this tool check?
This tool connects to your domain on port 443 and reads the SSL/TLS certificate presented. It reports the certificate validity dates, issuer, covered domains (Subject Alternative Names), TLS protocol version, and whether the certificate is trusted by standard certificate authorities.
What does "days remaining" mean operationally?
When a certificate expires, browsers and clients will immediately show trust errors — effectively taking your website or service offline for users who do not bypass the warning. Most certificate authorities recommend renewing at least 30 days before expiry. Automated certificate management (e.g. Let's Encrypt with ACME) can eliminate this risk entirely.
What is a self-signed certificate?
A self-signed certificate is issued by the same entity it identifies, rather than by a trusted Certificate Authority (CA). Browsers and clients do not trust self-signed certificates by default. They are appropriate for internal development or lab environments but should never be used on public-facing or client-accessible services.
Why does TLS version matter?
TLS 1.0 and 1.1 are deprecated and should not be used. TLS 1.2 is the current minimum acceptable version. TLS 1.3 is preferred for new deployments. Many compliance frameworks — including PCI-DSS, HIPAA technical safeguards, and NIST guidelines — explicitly require disabling legacy TLS versions.
What are Subject Alternative Names (SANs)?
SANs define all the domain names a certificate is valid for. Modern certificates use SANs rather than the Common Name (CN) for domain matching. A wildcard certificate (*.example.com) covers all subdomains at one level. A multi-domain certificate lists multiple specific domains.
This tool shows my certificate is valid but my browser still shows a warning — why?
Several factors not checked by this tool can cause browser warnings: intermediate certificate chain issues, HSTS misconfiguration, mixed content (HTTP resources loaded on HTTPS pages), or certificate mismatch (the domain you're visiting is not in the SAN list). Use browser developer tools or a full TLS audit to investigate further.
Related Operational Resources
Verify email authentication records and domain spoofing protections.
Full DNS diagnostic covering MX, NS, and email authentication records.
Ongoing infrastructure operations including certificate lifecycle management.
Align your TLS and certificate posture with HIPAA, SOC 2, and NIST requirements.
Operational Support
Need help managing your certificate infrastructure?
IT KORR can audit your SSL posture, coordinate certificate lifecycle management, and align your TLS configuration with your compliance requirements.
No commitment required — we respond within one business day.