Certificate Decoder

About Certificate Decoder

SSL Certificate Decoder – Instantly Decode and Analyze X.509 Certificates

Introduction to SSL Certificate Decoding

An SSL certificate decoder is a key tool for parsing and validating SSL/TLS certificates. It shows details like the issuer, subject, and expiration date. It's essential for checking certificate setups and spotting problems.

Decode Any SSL Certificate Online – Free and Secure

Our online SSL certificate decoder lets you upload or paste a certificate. It shows all the certificate's details in a clear format. It supports:

X.509 certificates in PEM, DER, and CER formats
Self-signed, CA-issued, and intermediate certificates
TLS/SSL, code signing, S/MIME, and other types

? Key Features:

100% browser-based decoding – no data sent to servers
Parses certificates issued by all major CAs
Supports multi-certificate chains
Instant validation of expiry dates, signature algorithms, and more
Ideal for troubleshooting SSL errors and verifying installations

How to Use the Online Certificate Decoder

Paste Certificate: Input your certificate in PEM format (beginning with -----BEGIN CERTIFICATE-----).
Click “Decode”: View all parsed data in a detailed format.
Review Fields: Check expiration, issuer, public key info, and more.

Example PEM Input:

-----BEGIN CERTIFICATE----- MIIFazCCA1OgAwIBAgISA1rjP... -----END CERTIFICATE-----

Parsed Certificate Output Fields Explained

Field	Description
Subject	Entity the certificate is issued to (e.g., domain or organization)
Issuer	Certificate Authority that issued the certificate
Serial Number	Unique ID for the certificate
Valid From / To	Start and expiry dates of the certificate
Signature Algorithm	Cryptographic algorithm used to sign the cert (e.g., SHA256-RSA)
Public Key Info	Key type and bit length (RSA 2048, ECC, etc.)
Extensions	Includes SAN (Subject Alternative Names), Key Usage, Basic Constraints
Fingerprint	Certificate hash used for verification

Example Output:

Subject: CN=www.example.com Issuer: CN=Let's Encrypt Authority X3 Valid From: Jan 01 00:00:00 2025 GMT Valid To: Mar 31 23:59:59 2025 GMT Signature Algorithm: sha256WithRSAEncryption Public Key: RSA (2048 Bits)

Use Cases for SSL Certificate Decoding

✅ Troubleshooting Installation Issues

Diagnose mismatched certificates, expired certs, or incorrect domain associations.

? Security Auditing

Check if certificate chains are valid and if they use the right encryption.

? CSR Verification

Make sure the decoded certificate matches the original Certificate Signing Request.

? Web Hosting & DevOps

Quickly check SSL details for hosted domains to prevent downtime or browser warnings.

Certificate Chain Decoding – Full Path Analysis

Our decoder supports multi-cert PEM files. It extracts all chain elements, including:

Root CA Certificate
Intermediate Certificate(s)
End-Entity (Leaf) Certificate

This full chain analysis ensures proper trust flow. It helps diagnose misconfigured chains.

graph TD A[Root CA] --> B[Intermediate CA] B --> C[Leaf Certificate]

Common Certificate Issues Detected by the Decoder

Issue	Description
Expired Certificate	Certificate validity has ended, causing trust errors.
Wrong Common Name (CN)	CN does not match the domain accessed by the user.
Missing SANs	Subject Alternative Names are not present or incomplete.
Weak Signature Algorithm	SHA-1 or other deprecated algorithms used.
Broken Chain	Missing intermediate or root certificates.

Supported Formats and Compatibility

Format	Extension	Supported
PEM	.pem, .crt, .cer	✅
DER	.der	✅
PFX/P12	.pfx, .p12	❌ (Not supported in browser)

Convert PFX or DER to PEM before decoding:

openssl pkcs12 -in certificate.pfx -out certificate.pem -nodes

Frequently Asked Questions (FAQs)

Can I decode certificates from websites directly?

No. Use browser tools or openssl s_client to extract and decode them manually.

Is it safe to decode sensitive certificates online?

Yes. Our tool is fully browser-based—no certificates are uploaded or logged.

What if the certificate has multiple entries?

The decoder will parse and display all entries sequentially, including intermediate certs.

Can I decode a self-signed certificate?

Yes. Self-signed certificates are parsed the same way as CA-issued ones.

Conclusion: Decode and Validate SSL Certificates Instantly

Our free SSL certificate decoder is a powerful tool for analyzing, verifying, and troubleshooting SSL/TLS certificates. It supports PEM and DER formats, multi-cert chains, and browser-based security. Paste your certificate, decode it instantly, and ensure your digital infrastructure is secure and compliant.