Free SSL Checker
An SSL checker connects to a target hostname over HTTPS, retrieves the presented X.509 certificate chain, validates expiry dates and chain of trust against trusted root CAs, enumerates supported TLS protocol versions and cipher suites, and assigns a security grade based on certificate health, protocol deprecation, and cryptographic strength.
Enter any domain name into ScanSuite's SSL checker and run the scan. The tool connects via TLS, displays certificate subject, issuer, validity dates, SAN entries, chain completeness, supported protocols, cipher suites, and an aggregate HTTPS security grade with prioritized remediation recommendations.
Introduction to SSL/TLS Certificate Validation
Transport Layer Security (TLS) encrypts data in transit between browsers and servers, authenticates server identity through X.509 certificates, and underpins trust for e-commerce, banking, healthcare, and every HTTPS API. Expired certificates, incomplete chains, weak cipher suites, and deprecated protocol versions cause browser warnings, service outages, and exploitable downgrade paths.
ScanSuite's free SSL checker performs remote TLS handshakes against any public hostname, extracting certificate details, validating the chain of trust, detecting imminent expiry, and grading overall HTTPS posture. Results help developers, security teams, and compliance auditors maintain continuous certificate hygiene without installing OpenSSL or sslyze locally.
Pair SSL scans with the security headers checker for HSTS validation, the CORS checker for API endpoint hardening, DNS lookup for certificate name mismatch investigation, and port scanner to confirm TLS services on non-standard ports.
What Is an SSL Checker?
An SSL checker (also called a TLS checker or certificate analyzer) initiates an HTTPS connection to a domain, captures the certificate presented during the TLS handshake, and evaluates it against security baselines. Checks include not-before and not-after validity windows, subject alternative name (SAN) coverage for the requested hostname, signature algorithm strength, and whether intermediate certificates form a complete chain to a trusted root CA.
ScanSuite enumerates negotiated TLS versions (TLS 1.0 through 1.3), flags deprecated SSLv3 and TLS 1.0/1.1 usage, lists supported cipher suites with forward secrecy and AEAD indicators, and detects common misconfigurations like SHA-1 signatures, RSA key sizes below 2048 bits, and missing OCSP stapling.
Letter grades aggregate certificate health, protocol support, cipher strength, and known vulnerability exposure (BEAST, POODLE, ROBOT) into a single score developers can track across deploy cycles and certificate renewals.
Why Check SSL/TLS Configuration Remotely?
Certificate problems often surface only from external vantage points. Internal monitoring may hit load balancer VIPs with valid certs while public clients receive expired or mismatched certificates on alternate paths through CDNs, failover nodes, or forgotten legacy subdomains discovered via DNS enumeration.
Automated SSL scanning catches expiry before browsers display interstitial warnings that erode user trust and trigger SEO penalties. ScanSuite alerts on certificates expiring within 30 and 7 days, incomplete intermediate chains that break Android and older browser trust, and hostname mismatches when SAN entries omit newly deployed subdomains.
Regular TLS audits complement email authentication checks with the SPF DKIM checker, security header analysis, and port scanning to map your complete encrypted attack surface.
Who Uses SSL Certificate Checkers?
DevOps and platform engineers monitor certificate expiry across production, staging, and microservice endpoints, integrating scan results into incident response when Let's Encrypt renewals fail silently.
Security analysts and compliance auditors document TLS posture for PCI-DSS, HIPAA, and SOC 2 assessments, recording cipher suite baselines and deprecated protocol elimination evidence.
Web developers troubleshoot mixed-content and certificate name mismatch errors after migrating domains, validating that new SAN entries cover all apex and www variants before cutover.
How the SSL Checker Works
When you submit a hostname, ScanSuite resolves DNS A and AAAA records, initiates a TLS connection on port 443 (or specified port), and retrieves the full certificate chain presented by the server during the handshake.
The analyzer parses X.509 fields: subject CN and SAN dNSName entries, issuer organization, serial number, signature algorithm, public key type and size, validity period, and key usage extensions. Chain validation walks from leaf certificate through intermediates to a trusted root in the Mozilla CA store.
Protocol and cipher enumeration uses controlled handshake probes to detect supported TLS versions and rank cipher suites by strength. The grading engine weights expired certificates and hostname mismatches as critical, deprecated protocols as high severity, and weak ciphers as medium, producing a percentage score mapped to letter grades A+ through F.
Healthy TLS Configuration Example
A well-configured site presents a valid leaf certificate with SAN entries covering example.com and www.example.com, signed by a trusted intermediate chaining to a public root CA.
The server negotiates TLS 1.3 with TLS_AES_256_GCM_SHA384 or TLS 1.2 with ECDHE-RSA-AES256-GCM-SHA384, providing forward secrecy and authenticated encryption.
HSTS header with max-age=31536000 and includeSubDomains appears in the security headers checker scan, complementing strong TLS configuration.
TLS Protocol Security Comparison
| Protocol | Status | Recommendation | |
|---|---|---|---|
| SSLv3 | Deprecated | Disable immediately; vulnerable to POODLE | |
| TLS 1.0 / 1.1 | Deprecated | Disable; non-compliant with PCI-DSS 4.0 | |
| TLS 1.2 | Acceptable | Minimum standard with strong cipher configuration | |
| TLS 1.3 | Preferred | Best performance and security; enable where supported |
Why Does My SSL Scan Show a Certificate Mismatch?
The requested hostname may not appear in the certificate SAN or CN fields. Add the hostname to your certificate request or deploy a certificate covering that subdomain.
CDN or reverse proxy SNI routing may serve a default certificate for unconfigured hostnames. Verify edge certificate mappings in your CDN dashboard.
Related tools
- Security Headers — Generate secure headers
- CSP Generator — Build Content Security Policy
- CORS Checker — Test CORS configuration
- Subdomain Finder — Map subdomains and validate certificates across discovered hostnames.
- Security Headers Checker — Verify HSTS and related HTTPS hardening headers after SSL validation.
- CORS Checker — Test cross-origin policies on HTTPS API endpoints.
- DNS Lookup — Resolve hostnames and investigate SAN mismatch via DNS records.
- Port Scanner — Discover TLS services on non-standard ports like 8443 or 9443.
- SPF DKIM Checker — Validate email authentication DNS records for the same domain.
- What Is My IP — Confirm your egress IP when debugging certificate pinning or firewall rules.
Frequently Asked Questions
What can this SSL checker show today?
It probes the URL from your browser (often via a limited no-cors fetch) and reports connectivity-oriented results. It does not display certificate issuer, SANs, expiry dates or a full TLS version matrix—use `openssl s_client` or your hosting panel for those details.
What is the difference between SSL and TLS?
TLS is the modern successor to SSL. The term SSL persists colloquially, but current sites should use TLS 1.2 or TLS 1.3 and disable TLS 1.0/1.1.
What does "certificate chain incomplete" mean?
The server is not sending the intermediate certificate(s). Some browsers and devices then cannot build a trusted chain. Install the full chain bundle from your certificate authority.
Why does my certificate show as expired or invalid?
It may have passed its expiry date, not cover the hostname you are visiting, be self-signed, or be missing intermediates. Automated renewal (such as Let's Encrypt with certbot) prevents expiry.
What is an SSL certificate?
An X.509 digital certificate binds a public key to a domain identity, signed by a Certificate Authority, enabling browsers to verify they are connecting to the legitimate server.
How do I check if my SSL certificate is expired?
Enter your domain in ScanSuite's SSL checker. The report displays not-before and not-after dates and flags certificates expiring within 30 days.
What is a certificate chain?
The chain includes your leaf certificate, one or more intermediate CA certificates, and ultimately chains to a trusted root CA stored in browser trust stores.
Why do browsers show "certificate not trusted"?
Common causes include expired certificates, hostname mismatches, self-signed certificates, or missing intermediate certificates in the server chain.
What are Subject Alternative Names (SAN)?
SAN entries list all domain names and IP addresses covered by a certificate. Modern browsers require hostname matches in SAN, not just the legacy CN field.
What cipher suites should I use?
Prefer TLS 1.3 AEAD ciphers or TLS 1.2 ECDHE suites with AES-GCM or ChaCha20-Poly1305 providing forward secrecy and authenticated encryption.
What is forward secrecy?
Forward secrecy (FS) ensures session keys cannot be decrypted later even if the server's long-term private key is compromised. ECDHE key exchange provides FS.
What is OCSP stapling?
OCSP stapling attaches fresh certificate revocation status to the TLS handshake, improving performance and privacy compared to client-side OCSP lookups.
How often should I scan SSL certificates?
Scan weekly for production domains and immediately after certificate renewals, CDN migrations, or DNS changes affecting HTTPS endpoints.
Does a wildcard certificate cover all subdomains?
A wildcard like *.example.com covers one subdomain level (api.example.com) but not nested subdomains (v2.api.example.com) or the bare apex domain.
What is HSTS and how does it relate to SSL?
HTTP Strict Transport Security forces browsers to use HTTPS only. It complements valid certificates by preventing protocol downgrade attacks.
Can I check SSL on non-standard ports?
Yes. Specify the port when scanning services like SMTPS (465), IMAPS (993), or custom HTTPS ports discovered via port scanning.
What SSL grade should I target?
Aim for A or A+ grades with valid certificates, TLS 1.2+ only, strong ciphers, and HSTS enabled. B grades indicate fixable weaknesses.
What happens when Let's Encrypt renewal fails?
The existing certificate remains valid until expiry, then browsers show trust errors. Monitor expiry dates and automate renewal verification with SSL scans.
Are self-signed certificates acceptable?
Self-signed certificates are fine for internal services but cause browser warnings on public websites. Use publicly trusted CAs for customer-facing domains.
What is certificate transparency?
CT logs publicly record issued certificates, enabling detection of unauthorized or misissued certs for your domains through monitoring services.
Is this SSL checker free?
Yes. ScanSuite provides unlimited free SSL/TLS scans on public hostnames without registration or daily caps.
What does an SSL checker test?
It connects to the hostname you enter and reports the certificate subject, issuer, expiry, and the TLS version the server negotiated. Use it to see a public certificate. It is not a full configuration audit of every cipher.
Summary
ScanSuite's free SSL checker validates TLS certificates, chain of trust, expiry dates, supported protocols, and cipher suites for any domain. Get HTTPS security grades, detect imminent certificate expiration, and receive actionable remediation guidance to maintain trusted encrypted connections.