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How to Decode SSL Certificates - Step by Step Guide

Step 1

Get Your SSL Certificate

First, you need to obtain the X.509 certificate you want to decode. These certificates follow the RFC 5280 standard for Public Key Infrastructure. There are several ways to get your certificate:

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From your server: Extract the certificate from your web server (Apache, Nginx, IIS)
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From a file: Upload a .pem, .crt, or .cer file directly
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From your browser: Export a certificate from your browser's security settings
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Try the sample: Click "Sample" to load an example certificate and see how it works

Example: PEM-Formatted Certificate

Certificates should be in PEM format with BEGIN and END markers:

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
Step 2

Paste Certificate and Auto-Decode

Simply paste your certificate into the decoder! The tool automatically parses the certificate using ASN.1 DER encoding and extracts all important information:

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Instant parsing: Certificate is decoded in real-time as you paste
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Validation: Automatically checks certificate format and validity
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All details extracted: Subject, issuer, dates, public key, extensions, and more

Example: Decoded Certificate Information

The decoder extracts and displays key certificate details from the GlobalSign Root CA:

Common Name: GlobalSign Root CA
Organization: GlobalSign nv-sa
Issuer: GlobalSign Root CA (Self-signed)
Valid From: Sep 1, 1998
Valid Until: Jan 28, 2028
Public Key: RSA 2048 bits
Signature: SHA1withRSA
Serial Number: 04:00:00:00:00:01:15:4b:5a:c3:94
Step 3

View Certificate Details

Explore comprehensive certificate information organized into clear sections:

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Subject & Issuer: See who the certificate belongs to and who issued it
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Validity Period: Check expiration dates and days remaining
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Public Key Info: View algorithm, key size, and technical details
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Extensions: See Subject Alternative Names (SANs), key usage, and constraints
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Fingerprints: Get SHA-256, SHA-1, and MD5 fingerprints for certificate pinning
Step 4

Export Certificate Information

Save the decoded certificate details for your records or documentation:

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Download as JSON: Export all certificate details in structured JSON format
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Copy fingerprints: Quick-copy SHA-256 or SHA-1 fingerprints for pinning
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Visual indicators: Color-coded validity status shows if certificate is expired or expiring soon

Frequently Asked Questions

What is an SSL certificate decoder?

An SSL certificate decoder is a tool that parses X.509 certificates and displays their contents in human-readable format. It extracts information like subject, issuer, validity dates, public key details, extensions, and fingerprints from PEM-encoded certificates following industry standards.

What certificate formats are supported?

The decoder supports PEM-formatted certificates (Base64-encoded with BEGIN/END markers). Common file extensions include .pem, .crt, .cer, and .txt. If you have a DER-formatted certificate, you'll need to convert it to PEM format first.

Is it safe to decode my SSL certificate online?

Yes! SSL certificates are public information by design and contain no sensitive data. Your certificate is processed entirely in your browser using client-side JavaScript - nothing is sent to our servers. Learn more about digital certificates and TLS security. However, never share or decode private keys online.

How do I check if my SSL certificate is expired?

Paste your certificate into the decoder and look at the Validity Period section. The tool shows the expiration date and calculates days remaining. Expired certificates are highlighted in red, and certificates expiring within 30 days show in yellow.

What are certificate fingerprints used for?

Certificate fingerprints (SHA-256, SHA-1, MD5) are cryptographic hashes that uniquely identify a certificate. They're used for certificate pinning in mobile apps, verifying certificate identity, and comparing certificates. Our decoder displays all fingerprints with easy copy buttons.

Can I decode certificate chains?

Currently, the decoder processes one certificate at a time. If you have a certificate chain (multiple certificates), paste each certificate individually to view its details. The tool will show the issuer information to help you understand the chain hierarchy.

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