Is your HTTPS certificate valid?
Type a domain and we’ll open one secure connection to it, read its certificate and tell you in plain words whether browsers trust it, which names it covers and when it expires. Free, no sign-up, and we don’t keep what you type.
Nothing checked yet
Your report shows up here: whether the certificate is trusted, the names it covers, when it expires and what to do next.
What this checks
- Whether browsers trust the certificate, checked against the same authorities they use.
- Whether it covers the exact name you typed, wildcards included, and the other names on it.
- When it started, when it expires and how many days are left.
- The chain of certificates the server sends and who issued each one.
- The TLS version and cipher of the connection, plus the key type and size.
- CAA records that limit which authorities may issue certificates.
We open at most two connections to port 443 of the site’s public address, send nothing after the handshake and close it. Private and reserved addresses are never contacted.
What we keep
Only a daily count of how many checks ran and how they ended. Not what you typed, not your address, no cookies.
Questions people ask
What does an SSL certificate actually do?
It proves to browsers that they’re talking to the real site and lets the connection be encrypted. Without a valid one, browsers show a warning before the page and many visitors leave. “SSL” is the old name; today’s connections use TLS, but the certificates are the same thing.
Why does my certificate work for example.com but not www.example.com?
A certificate only covers the names listed on it. www.example.com and example.com are two names, so the certificate needs both, or a wildcard such as *.example.com for the www name. Tick “Also check the www name” to test both at once.
My certificate is valid, but some phones say it isn’t trusted. Why?
Usually the server sends your certificate without the intermediate certificate that links it to a trusted authority. Desktop browsers often fetch the missing piece themselves; many phones and apps don’t. Installing the full chain fixes it.
How often do certificates need renewing?
Public certificates last at most about a year, and many (Let’s Encrypt’s, for example) last 90 days and renew automatically. The limits are getting shorter, so automatic renewal matters more every year.