How to Check SSL Certificate

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An SSL certificate contains critical information: the domain name(s) it covers (subject and SAN), the issuing certificate authority, the validity period, the public key, and the signature algorithm used to verify its authenticity.

An expired or misconfigured SSL certificate can have severe consequences. Browsers display prominent warning pages that scare visitors away, killing trust and conversions. Search engines penalize sites with invalid certificates. For e-commerce sites, a failed certificate means payment pages are blocked, causing direct revenue loss.

Beyond expiration, you need to verify that your certificate uses strong encryption standards. Weak signature algorithms (like SHA-1) and short key lengths (under 2048 bits) are no longer considered secure and may trigger browser warnings. Checking your certificate's details helps you stay ahead of expirations and maintain strong security posture.

WebCheckly provides comprehensive SSL certificate detection in two ways:

One-time scan:pages.guides.sslCertificate.s3P1Text

Continuous monitoring: Set up an SSL monitor to check your certificate automatically on a schedule (daily or weekly). You'll get alerts before the certificate expires, so you never miss a renewal.

The SSL check reveals: certificate issuer and subject, validity period with remaining days countdown, signature algorithm and key strength, DNS names (Subject Alternative Names / SAN), and certificate status (valid or invalid).

• Set up expiry monitoring: Don't rely on memory. Configure automatic SSL certificate monitoring with alerts at 30, 14, and 7 days before expiry.
• Use strong certificates: Ensure your certificate uses at least SHA-256 signature algorithm and a 2048-bit or higher RSA key.
• Verify SAN coverage: Make sure all subdomains your site uses are covered by the certificate's SAN list.
• Check after renewal: New certificates should be verified immediately to confirm they're properly installed.
• Monitor from outside your network: Internal checks might show a valid certificate that external users can't verify.

WebCheckly's SSL detection gives you complete visibility into your certificate configuration. The one-time scanner provides instant detailed information, while continuous monitoring watches your certificates day and night — sending alerts when expiration is approaching or if the certificate becomes invalid. Combined with domain expiry monitoring, you can prevent both SSL and domain registration lapses that would take your site offline.