Free tool · No sign-up · Server-assisted
SSL Certificate Checker
Check a domain's TLS certificate: who issued it, when it expires, how many days are left, which hostnames it covers, and whether the chain to a trusted root is intact. Catches the two failures that take a site down without warning — an expired certificate and a name it does not actually cover.
Server-assisted · we open a TLS connection to the host on port 443 and read back its certificate
Method & assumptions
- This is a server-assisted tool: a browser cannot inspect a raw certificate, so our server completes a TLS handshake to the host on port 443 and reads back what it presents.
- Only the host you enter is sent, and only to our server, which connects once. Nothing is stored.
- Certificate validation is turned off for the read, on purpose — that is the only way to report an expired or mismatched certificate rather than just failing. The trust result above reflects standard validation separately.
- Hostname coverage honours wildcard rules: *.example.com covers a.example.com, but not example.com or a.b.example.com.
Plate —Other tools
More on the bench
- 01DNS LookupEvery record for a domain, from your browser.
- 02SPF, DKIM & DMARC CheckerIs your domain safe to spoof?
- 03Supabase Security AuditorPoint it at your project, find the holes.
- 04JWT DecoderPaste a token, read what is inside.
- 05Secret & .env ScannerPaste code or a .env, catch the leaked keys.
- 06Security Headers ScannerEnter a URL, grade its headers.
- 07CORS TesterSee exactly what a URL allows cross-origin.
- 08Base64 Encode / DecodeText or files, both directions.
Free diagnosticsSame-day dispatchNamed techniciansDone or free
Need it built, not just checkedWe write the software
We write the software
behind tools like these
Anyone who has ever been paged because a certificate expired at 2am on a Sunday.