What is an SSL Certificate?

SSL (Secure Sockets Layer) and its modern successor TLS (Transport Layer Security) are cryptographic protocols that encrypt data between browsers and servers. HTTPS is HTTP over TLS — that little padlock in your browser address bar. Without HTTPS: passwords, credit cards, personal data travel as plain text, easily intercepted on public WiFi. With HTTPS: data is encrypted, identity is verified, integrity is guaranteed. Modern browsers flag non-HTTPS sites as ‘Not Secure’. Google penalizes them in search rankings. This tool quickly verifies if a domain has working HTTPS, then links to detailed certificate analysis (SSL Labs grade, certificate chain, expiration, cipher strength).

How to use this tool

1. Enter domain — Just domain (example.com) — no protocol prefix.
2. Click Check SSL — Tool tests HTTPS connectivity.
3. View status — Valid HTTPS = ready for production. Failed = needs certificate fix.
4. Get detailed analysis — Click linked SSL Labs or crt.sh for cipher details, certificate chain, expiration.

What HTTPS protects

SSL/TLS provides three guarantees:

• Confidentiality: Data is encrypted — eavesdroppers can't read it
• Integrity: Data can't be modified in transit (MITM attacks blocked)
• Authentication: The server is who it claims to be (certificate verified by trusted CA)

How it works (simplified):

1. Browser connects to server requesting HTTPS
2. Server sends certificate (public key + identity + signed by CA)
3. Browser verifies CA signature against trusted CA list
4. Browser generates session key, encrypts with server's public key
5. Server decrypts with private key, both now have shared session key
6. All further communication encrypted with session key

Certificate Authorities (CAs):

• Let's Encrypt: Free, automated, 90-day certificates — powers most modern HTTPS
• DigiCert, Sectigo, GoDaddy: Paid CAs with extended validation options
• Cloudflare: Free SSL for sites behind their CDN

Examples

• google.com: Valid SSL, certificate by Google Trust Services, TLS 1.3
• example.com: Valid SSL, multiple SAN entries (covers many subdomains)
• Expired certificate: Browser shows ‘Your connection is not private’ warning
• Self-signed cert: Works but browser warns — not trusted by CA
• Mixed content: HTTPS page loading HTTP images — partial trust, browsers flag
• Wildcard cert: *.example.com covers all subdomains (api.example.com, www.example.com)

Tips & best practices

• Use Let's Encrypt for free SSL — trusted, auto-renewed via certbot or Cloudflare
• Always run SSL Labs SSL Test for comprehensive grade (A+ is ideal)
• Enable HTTPS, then enforce it: redirect HTTP → HTTPS in your server config
• Add HSTS header: Strict-Transport-Security: max-age=31536000
• Monitor certificate expiration — auto-renewal via Let's Encrypt prevents surprises
• Use TLS 1.2 or 1.3 only — disable TLS 1.0 / 1.1 (deprecated, insecure)
• Strong cipher suites: avoid RC4, 3DES, weak DH parameters

Limitations & notes

This tool checks connectivity only — doesn't show certificate details, cipher info, or expiration date. For full analysis use SSL Labs SSL Test (mostly free), crt.sh (transparency logs), or browser DevTools Security tab. CORS proxy may not accurately reflect certain SSL issues — for production verification, browser test from multiple locations recommended.

Frequently Asked Questions

What's the difference between SSL and TLS?

SSL is the older protocol (1.0, 2.0, 3.0). TLS is the newer version (1.0, 1.1, 1.2, 1.3). ‘SSL’ is commonly used as a generic term, but modern certificates are actually TLS. SSL 2.0/3.0 are deprecated and insecure.

How long do SSL certificates last?

Let's Encrypt: 90 days (auto-renew). Commercial CAs: 1-2 years (Apple/Google now require max 1 year). Industry trend toward shorter lifespans for security.

Is Let's Encrypt as secure as paid certificates?

Cryptographically identical. The validation level differs: Let's Encrypt does Domain Validation (DV). Paid options offer Organization Validation (OV) and Extended Validation (EV) with more rigorous identity checks — useful for banks, e-commerce.

Why does my site say ‘Not Secure’?

Either no SSL configured, expired certificate, self-signed (not trusted by CA), wrong domain on certificate, or mixed content (HTTPS page loading HTTP resources).

How do I add HTTPS to my WordPress site?

Most hosts (Hostinger, Bluehost, SiteGround) offer one-click SSL via Let's Encrypt. After installation, install plugin ‘Really Simple SSL’ to force HTTPS everywhere.

What’s an SSL grade and how do I improve it?

SSL Labs grades A+ to F based on protocol support, cipher strength, vulnerability mitigation. To improve: enable TLS 1.3, disable old protocols, use modern ciphers, enable HSTS, add OCSP stapling.

Can I use one SSL certificate for multiple domains?

Yes — SAN (Subject Alternative Name) certificates cover up to 100+ domains. Wildcard certificates cover all subdomains (*.example.com). Modern Let's Encrypt supports both.

Related tools

HTTP Headers Checker · Domain Age Checker · Redirect Checker