Certificate Checker
Certificate Checker parses a PEM certificate, CSR, or key in your browser and shows the subject, issuer, validity, days to expiry, and serial.
Certificate Checker is a browser-based web developer tool on WebDevToolsBase. Certificate Checker parses a PEM certificate, CSR, or key in your browser and shows the subject, issuer, validity, days to expiry, and serial. To use it, paste your input and view the result directly in your browser — no signup and nothing to install.
Certificate Checker is a free SSL & HTTPS Tools utility that runs entirely in your browser — nothing you enter is uploaded.
How to use Certificate Checker
- Paste the text you need to check into the input box.
- Set Paste a PEM certificate (BEGIN/END lines) so the output fits your use case.
- Certificate Checker updates the output automatically as you type.
- When it looks right, Copy to save it.
About this tool
There is no server behind Certificate Checker. Certificate Checker parses the X.509 fields of a certificate you paste, locally.
Nothing about the certificate is transmitted. Nothing you enter is uploaded, and it keeps working offline once the page has loaded.
Frequently asked questions
How do I use Certificate Checker?
Use Certificate Checker to check your input without installing anything using the Paste a PEM certificate (BEGIN/END lines) control; everything happens client-side.
Does Certificate Checker cost anything?
No — Certificate Checker is completely free, with no sign-up and no hidden limits.
Does Certificate Checker upload my data?
No — Certificate Checker processes everything locally in your browser, so nothing you enter is uploaded or stored.
How do I inspect a live site's certificate with Certificate Checker?
Export the certificate from your browser's padlock as PEM and paste it into Certificate Checker; it decodes the fields locally.
Does Certificate Checker work offline?
Once the page has loaded, Certificate Checker keeps working with no network connection.