TLS & Certificate Checker

Description

- Negotiated TLS version, cipher suite and certificate expiry for any public domain.
- Catches expired certificates before your users do. Internal hosts are blocked.
- Note: this tool displays certificate data (including expired or self-signed certs) but does not validate the chain of trust — a shown certificate is not necessarily trusted.
- Only supports GET request.
- Limit : 30 requests per minute. Once reached subsequent requests will result in error 429 (too many requests) until your quota is cleared.

Endpoint - Check TLS certificate

HTTP Request:
GET /v1/tls?domain=example.com
Optional port (default 443).
Examples
/v1/tls?domain=example.com
/v1/tls?domain=expired.badssl.com
response

{
  "domain": "example.com",
  "port": 443,
  "tls_version": "TLSv1.3",
  "cipher": "TLS_AES_256_GCM_SHA384",
  "cert_subject": "CN=example.com",
  "cert_issuer": "C=US, O=SSL Corporation, CN=Cloudflare TLS Issuing ECC CA 3",
  "not_before": "2026-07-29T22:10:08Z",
  "not_after": "2026-10-27T22:17:21Z",
  "days_left": 34,
  "expired": false
}