SSL/TLS Certificate Checker
Look up the leaf certificate served by any host on any TCP port. See the subject, issuer, validity window, Subject Alternative Names, signature algorithm, public key, the full chain of intermediates, and the SHA-256 fingerprint.
Related reading
- How to check an SSL/TLS certificate (and what to look for)Every HTTPS site relies on a TLS certificate. Here's how to read one, what each field actually means, and the things that should make you suspicious.
- How to read an open port (and when to actually worry)An 'open port' isn't a vulnerability by itself — it's information. Here's how to tell whether a port being open is fine, suspicious, or actively dangerous, and what to do about each case.
- DMARC, SPF, and DKIM explained (and why you need all three)Email spoofing is trivially easy without email authentication. Here's how SPF, DKIM, and DMARC work together — and how to check yours.