DeveloperFree browser tool

Certificate Decoder – Decode SSL Certificates

Decode X.509 SSL certificates. View certificate details and validity information.

No sign-upMobile readyPrivate by default
DEV

Tool

Enter your values and get results instantly.

HOW

How to Use

  1. 1Paste certificate in PEM format
  2. 2Click Decode
  3. 3View certificate details
WIN

Benefits

PEM format support
All fields shown
Validity check
Free
Browser-based
FAQ

Frequently Asked Questions

What information can I see from a decoded certificate?

You can view the issuer, subject, validity period (not before / not after), serial number, and the raw certificate structure in a readable format.

What format should the certificate be in?

PEM format – the text that starts with -----BEGIN CERTIFICATE----- and ends with -----END CERTIFICATE-----. This is the standard format for web servers.

Can I decode a certificate from any website?

Yes – you can export a site's certificate from your browser and paste it here to inspect its details.

Will this tool verify if a certificate is valid?

It shows the validity dates so you can check if the certificate has expired, but it does not perform online revocation checks.

Is the certificate data sent to a server?

No – decoding happens entirely in your browser. Your certificate never leaves your device.