Few things damage user trust faster than a "Your connection is not private" browser security warning. If your website's SSL (Secure Sockets Layer) or TLS (Transport Layer Security) certificate expires, browsers will block users from accessing your site, resulting in lost traffic and revenue.
While modern certificate authorities have simplified issuance, monitoring your certificate's expiration dates and validity remains a critical DevOps task.
This guide explains how to monitor SSL certificates and verify certificate metadata.
1. The Cost of SSL Expiration
An SSL/TLS certificate encrypts the traffic between the user's browser and your server, validating that the user is communicating with the real site rather than an impersonator.
If a certificate expires:
- Browsers block access: Chrome, Safari, and Firefox display prominent fullscreen security warnings that scare away users.
- APIs break: Mobile applications and external webhooks integrations will reject connection requests, causing service outages.
- SEO degradation: Google prefers HTTPS sites; prolonged security failures can impact search rankings.
2. Reading SSL Certificate Details
When auditing your site's HTTPS configuration, check these properties:
- Expiration Date: Note the exact days remaining. Modern Let's Encrypt certificates are only valid for 90 days, requiring automated renewal.
- Subject Alternative Names (SANs): Verify that all subdomain variants (e.g.
yourdomain.com,www.yourdomain.com,app.yourdomain.com) are declared on the certificate. - Issuer Certificate Authority: Confirm the certificate was issued by a trusted root authority (such as Let's Encrypt, Cloudflare, DigiCert).
- OCSP Stapling: Ensures the browser can verify the certificate status quickly without querying the certificate authority on every connection.
3. Auditing Your SSL Status
Instead of waiting for a browser warning, you can check your certificate parameters proactively.
Use the SSL Certificate Checker to verify domain certs. It retrieves the live certificate, counts the exact days remaining until expiration, lists all registered subdomains, verifies key algorithms, and checks root chain issuers.
- Audit your SSL certificate: SSL Certificate Checker