SSL Certificate Checker
Check SSL/TLS certificate expiry dates and create calendar reminders to renew before expiration.
Checking certificate...
📅 Set Renewal Reminder
Create a calendar event 1 month before the certificate expires to remind you to renew.
Bulk Certificate Check
| Domain | Status | Expires | Days Left | Issuer |
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What Does an SSL Certificate Checker Do?
An SSL/TLS certificate checker retrieves the digital certificate from a domain and analyzes its key properties: expiration date, issuing Certificate Authority, Subject Alternative Names (SANs), cipher suite support, and the full certificate chain. This lets you verify a certificate is valid, properly configured, and not about to expire — without needing command-line tools.
TLS certificates are how browsers verify that a website is actually operated by who it claims to be. They also enable encrypted HTTPS connections. An expired, mismatched, or misconfigured certificate causes browser security warnings that drive away users and break API integrations.
How to Use This Tool
- Enter a domain name (e.g.,
example.com) — no need to includehttps://. - Click Check SSL.
- Review the certificate details: expiry date, issuer, SANs, and chain validity.
Key Certificate Properties Explained
- Valid From / Valid To — The certificate's active period. Modern certificates are issued for 90 days (Let's Encrypt) to 1 year (commercial CAs).
- Subject Alternative Names (SANs) — The domains this certificate is valid for. A certificate for
example.commust haveexample.comin its SAN list (or as the Common Name) to be trusted. - Issuer / Certificate Authority — Who signed the certificate. Common CAs: Let's Encrypt (free, automated), DigiCert, Sectigo, GlobalSign.
- Certificate Chain — Certificates are verified through a chain from root CA → intermediate CA → end-entity certificate. A broken chain causes SSL errors.
- OCSP Stapling — Allows a server to include proof of certificate validity in the TLS handshake, improving performance and privacy over traditional OCSP checks.
Common SSL Certificate Errors
- ERR_CERT_DATE_INVALID — Certificate has expired. Renew immediately.
- ERR_CERT_COMMON_NAME_INVALID — Certificate hostname doesn't match. Check SANs.
- ERR_CERT_AUTHORITY_INVALID — Issuing CA not trusted. Usually a self-signed or intermediate chain issue.
- ERR_SSL_VERSION_OR_CIPHER_MISMATCH — Server using deprecated TLS version (TLS 1.0/1.1) or weak cipher suite.
Frequently Asked Questions
SSL (Secure Sockets Layer) is the predecessor to TLS (Transport Layer Security). SSL 2.0 and 3.0 are completely broken and disabled in all modern software. TLS 1.0 and 1.1 are deprecated and also disabled by most browsers. The current standards are TLS 1.2 and TLS 1.3. Despite this, "SSL certificate" and "SSL checker" remain the colloquial terms — the certificates themselves haven't changed, only the handshake protocol.
Browsers display a full-page security warning blocking access. API integrations throw SSL errors and fail. SEO rankings can drop. E-commerce transactions stop. Setting up automated renewal (Let's Encrypt + certbot/ACME, or a CDN with auto-renewal) eliminates this risk. Monitor expiry dates and set alerts at 30 and 7 days before expiration.
A wildcard certificate covers a domain and all its immediate subdomains. A certificate for
*.example.com is valid for www.example.com, api.example.com, mail.example.com, etc. It does NOT cover example.com itself (you need a SAN entry for that) or nested subdomains like sub.api.example.com.DV (Domain Validation) — CA only verifies domain ownership. Issued in minutes. Used by Let's Encrypt. No organization information in certificate. OV (Organization Validation) — CA verifies domain ownership + legal organization identity. Shows company name in certificate details. EV (Extended Validation) — Strictest verification, historically showed a green bar in browsers. Browsers removed EV visual indicators in 2019, making EV certificates largely obsolete for their primary differentiator.
CDN providers (Cloudflare, Fastly, AWS CloudFront) terminate TLS at their edge nodes and serve their own certificates. You'll see a Cloudflare or Amazon certificate instead of your origin certificate. This is normal — your connection to the CDN edge is encrypted with their cert, and the CDN-to-origin connection may use a separate certificate. Check your CDN's SSL settings if you want to ensure end-to-end encryption with your own certificate.