Check SSL/TLS certificate details for any domain via public certificate APIs. View issuer, validity period, days remaining, and SANs. Expiry alerts catch outages before users do — free, no signup. Uses cloud-based processing.
Content reviewed October 2026 · About Toolzum
Check a host over HTTPS from your browser — SSL/TLS reachability (which proves the browser validated the certificate chain) plus public issuance history (issuer, expiry, cert count) via crt.sh. No cipher-suite or protocol-version scan: browsers do not expose handshakes.
Decode and view SSL certificate details including subject, issuer, and validity period. Code never leaves your device — formatting and validation run locally in your browser.
Discover subdomains via public certificate records plus live DNS checks of common names. Read-only lookups run from your browser — the domain you check is visible to crt.sh and Google DNS, as with any lookup.
Validate IBAN structure, length, and mod-97 check digits for 80+ countries. Catch transfer typos before money moves — local ibantools work, free, no signup.
Convert any date to its day-of-year number (1–365/366) with days remaining. Developers compute ordinal dates for logs and filenames — free, no signup, runs locally.
Certificate issuer (e.g., Let's Encrypt, DigiCert), validity period (not-before and not-after dates), days remaining until expiration, serial number, and Subject Alternative Names (SANs).
Yes. The tool shows the exact expiration date and calculates days remaining. Use this to monitor your own domains or verify a site's certificate is current.
It shows chain entries when the certificate API returns them. The transparency-log fallback carries no live chain — confirm expiry against the live server before acting.
A SAN is an additional domain name or IP address covered by the same certificate. Many certificates secure multiple domains (e.g., example.com and www.example.com) via SANs.
No. Your browser queries third-party certificate APIs (ssl-checker.io with a crt.sh fallback), so the checked domain is visible to those providers. No search history is stored on our server.
Fewer than 30 days remaining reads Expiring, below 0 reads Expired. Each provider gets 15 seconds before the fallback runs, and the recent-checks row keeps your last 5 domains.
SSL/TLS Checker
Check a host over HTTPS from your browser — SSL/TLS reachability (which proves the browser validated the certificate chain) plus public issuance history (issuer, expiry, cert count) via crt.sh. No cipher-suite or protocol-version scan: browsers do not expose handshakes.
SSL Certificate Decoder
Decode and view SSL certificate details including subject, issuer, and validity period. Code never leaves your device — formatting and validation run locally in your browser.