How to use OpenSSL Test Certificate
- Add a PEM certificate to OpenSSL Test Certificate to get started.
- Press Parse certificate to run it locally in your browser.
- Read the subject, issuer, validity dates and expiry that OpenSSL Test Certificate lays out for you.
About this tool
OpenSSL Test Certificate runs entirely in your browser. OpenSSL Test Certificate decodes a pasted PEM certificate by walking its ASN.1/DER structure locally to read subject, issuer, validity window and serial.
The expiry countdown is computed locally, and nothing about the certificate is transmitted. No data is sent anywhere, so it stays fast and private by default.
Frequently asked questions
What does OpenSSL Test Certificate do?
OpenSSL Test Certificate runs entirely on your device: add your input, and it checks it locally in real time.
Do I need an account for OpenSSL Test Certificate?
No — OpenSSL Test Certificate needs no account, sign-up or installation.
Does OpenSSL Test Certificate upload my data?
No — OpenSSL Test Certificate processes everything locally in your browser, so nothing you enter is uploaded or stored.
How do I inspect a live site's certificate in OpenSSL Test Certificate?
Export the certificate from your browser's padlock as PEM and paste it into OpenSSL Test Certificate; it decodes the ASN.1/DER fields entirely on your device.
Does OpenSSL Test Certificate work offline?
Once the page has loaded, OpenSSL Test Certificate keeps working with no network connection.