SerpCrest
Free & open source

SSL / TLS Certificate Checker

Check a domain's real SSL certificate: validity, days until expiry, and issuer, via a live handshake rather than a cached estimate.

Useful right after a renewal or migration: a certificate that silently expired or swapped issuers is downtime or a browser warning waiting to happen, not something you find out about until a visitor complains.

20
Checks per minute
8s
Handshake timeout
Live
Not cached
0
Signup required
Certificate auditorLive handshake

How it works

1

Enter a domain

Just the domain, e.g. example.com - no need to include https:// or a path.

2

We open a real TLS connection

The server dials port 443 on that host directly via a live handshake and reads back the certificate chain. Nothing is estimated or cached.

3

Read the verdict

Validity, days until expiry, issuer, and the exact validity window - plus a warning if the certificate is invalid or expiring within 30 days.

Questions

Any valid certificate with 30 days or fewer left before it expires - the same threshold most browsers and monitoring tools treat as urgent.

Usually the host isn't listening on port 443, doesn't support TLS on that port, or the connection timed out - the message under the result explains which. A firewall blocking the request or an HTTP-only site are common causes.

Live. Every check opens a fresh TLS handshake to the domain you enter; nothing about the certificate is stored or reused between checks.

Yes, up to 20 checks per minute, to keep the live handshake connection from being abused. Wait a minute and try again if you hit that limit.

Redirects. Every old address should point to its new one in a single hop, which the redirect and canonical checker tests for up to 100 URLs. What Google says happens to your backlinks in a move is in our post on domain migrations.

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Run this on every link you own.

SerpCrest re-checks the placements in your projects every week and tells you when one breaks or disappears.