What is an SSL Checker?
An SSL/TLS certificate is what makes a site load as https:// — and an expired or misconfigured one greets every visitor with a full-page browser warning instead of your site.
This checker performs a real TLS handshake with the domain and reports what browsers will see: whether the certificate verifies, when it expires, who issued it, the TLS version and the chain.
The failure modes worth knowing: expired certificates (the most common outage — automation exists, use it), a missing intermediate certificate (works in Chrome which fixes chains, fails on older Android and many API clients), and name mismatch (certificate covers www but not the apex, or a forgotten subdomain). Each shows differently here.
How to use the SSL Checker
- Enter a domain.
- Press Check SSL.
- Review validity, days left, issuer and chain — expiring-soon certificates are flagged.
Frequently asked questions
How do I automate renewal?
Let's Encrypt with certbot or acme.sh renews free certificates automatically; most CDNs and hosts (Cloudflare, Netlify, cPanel AutoSSL) now handle it for you. Manual renewal is the outage generator.
Does the certificate affect SEO?
HTTPS is a confirmed ranking signal, and browsers mark HTTP as Not Secure — an expired certificate interstitial turns visitors away instantly.
How often do certificates expire?
Public certificates now last at most ~398 days, and Let’s Encrypt certificates 90 days — which is why automation (or at least expiry monitoring) matters.
The tool says invalid but my site loads for me — how?
Your browser may have a cached exception, or the failure is partial (for example a missing intermediate certificate that some devices tolerate). Treat invalid as urgent regardless.
What is the certificate chain?
The links from your certificate up to a trusted root authority. If an intermediate link is missing on the server, some clients fail even when your own certificate is fine.
Does the check change anything on my site?
No — it is a read-only handshake, exactly like a browser visiting your site.