Free SSL Certificate Checker

Verify SSL/TLS certificate validity, expiry, issuer, and covered domains. Get an instant A-F security grade. Uses Certificate Transparency logs plus a live HTTPS probe — no signup required.

Who uses this tool?

Operations teams — monitor cert expiry across production domains
Security auditors — verify cert chain, issuer CA, and wildcard scope
DevOps & SRE — confirm HTTPS is serving after a cert renewal
Compliance teams — document active certs for audits (PCI DSS, SOC 2, ISO 27001)
Domain owners — see when the next renewal is due

How to use (step-by-step)

Step 1 — Enter a domain: Type the domain (github.com, example.org, etc.) into the search box.
Step 2 — Click Check: We query CT logs for the most recent cert and probe HTTPS to confirm it is actually serving.
Step 3 — Read the grade: A-F grade based on days until expiry + HTTPS health. See full cert details, all covered domains (SANs), and wildcard status.

Frequently asked questions

What does the SSL checker actually verify?

It verifies the active SSL/TLS certificate for a domain: issuer, issue date, expiry date, covered hostnames (SANs), wildcard status, and whether HTTPS is actually serving correctly. Data comes from Certificate Transparency logs plus a live HTTPS request.

What is a Certificate Transparency log?

Certificate Transparency (CT) is an open log of every SSL certificate ever issued by a public CA. Browsers require certs to be CT-logged since 2018 — it lets anyone verify who issued what, making mis-issuance impossible to hide.

How is the SSL grade calculated?

Grade A: valid, >90 days until expiry, HTTPS serving. Grade B: expires within 90 days. Grade C: expires within 30 days. Grade D: expires within 7 days. Grade F: expired, or HTTPS not serving at all.

Why does it say Lets Encrypt?

Lets Encrypt is a free certificate authority that issues 90-day certs (auto-renewed). It is the most widely used CA on the web — being issued by Lets Encrypt is a positive signal, not a warning.

Related free tools

HTTP Headers Checker — Security score and CDN detection
Redirect Chain Checker — Trace 301/302 hops
DNS Lookup — A, MX, CAA records
WHOIS Lookup — Domain registrar and expiry
All Free Domain Tools — Complete toolkit for domain research

Try it on popular domains: github.com, google.com, cloudflare.com, openai.com.