What I Built
SSL Certificate Checker — enter any domain, get full SSL certificate details.
What it shows:
- Validity status — Valid, Expiring Soon, or Expired
- Days remaining until expiry
- Issuer — who issued the certificate (Let's Encrypt, DigiCert, etc.)
- Protocol — TLS 1.2 or 1.3
- Key size — 256-bit, 2048-bit, etc.
- Serial number and fingerprint
- Subject Alternative Names (SANs) — all domains covered by the cert
How it works:
The API opens a raw TLS connection to the target domain, extracts the peer certificate, and returns all the details. No HTTP request needed — it checks the actual TLS handshake.
Use cases:
- Check if your SSL is about to expire
- Verify cert issuer after migration
- Debug SSL issues (wrong SANs, expired certs)
- Audit third-party domains
Try It
https://sslcheck-zeta.vercel.app
Free. No signup. Works with any domain.
Part of my free developer tools collection. More at manja316.gumroad.com
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