Certificate Expiration Checker

Paste a PEM certificate and see the not-before and not-after dates, plus how many days are left, before a renewal quietly slips past.

How to use
  1. Paste the PEM certificate block.
  2. The validity window is parsed and displayed.
  3. Read the days remaining before expiry.
Frequently asked questions
What do not-before and not-after mean?
The window the certificate is valid for. Not-before is when it starts being accepted, not-after is the moment browsers begin rejecting it.
Where do I get the PEM text?
From your certificate file, or by running openssl s_client against the host and copying the block between BEGIN and END CERTIFICATE.
Does this check the certificate is trusted?
No, it reads the dates in the certificate itself. Chain validation and revocation status are separate questions this does not answer.
When should I renew?
Thirty days out is the usual trigger, and it is what most automated renewals use. It leaves room for a failed renewal without an outage.
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