Certificate Expiration Checker
Check when a certificate expires and how many days remain. Paste your data, then click to dissect it. Everything runs on your device, nothing is sent to a server.
Everything runs in your browser. Your data is never sent to our servers.
Example
Example Input
-----BEGIN CERTIFICATE-----…
Example Output
✓ VALID — expires in 312 days
How to Use
- 1Paste your data (PEM/Base64/token) into the Input field.
- 2Click the button (or press Ctrl+Enter) to dissect it.
- 3Read the decoded result in the Output field.
About Certificate Expiration Checker
Expired certificates are a common cause of site outages (browsers reject HTTPS). Checking validity early prevents those surprises.
This tool parses a PEM/DER certificate and shows the "valid until" date, whether it has expired, and the number of days remaining until (or since) expiry.
Use it for a quick audit of your certificate. For all details (subject, issuer, algorithms), use the X.509 Certificate Viewer.
FAQ
Are my data or keys sent to a server?
No. Certificate Expiration Checker runs entirely in your browser using the Web Crypto API and client-side libraries. Your data, passwords, and keys never leave your device.