SSL Certificate Decoder
Decode raw PEM X.509 certificates locally to inspect public keys and validity attributes.
PEM Certificate Input
About SSL Certificate Decoder
The SSL/TLS X.509 Certificate Decoder parses PEM-encoded certificates (`-----BEGIN CERTIFICATE-----`), CSRs, and public keys, extracting the Subject Common Name (CN), Subject Alternative Names (SANs), Issuer CA, Validity Period, Serial Number, and SHA-256 Fingerprints.
How to Use SSL Certificate Decoder
Step 1
Paste your PEM-formatted certificate or CSR into the editor.
Step 2
View the parsed certificate anatomy and validity timeline in real time.
Step 3
Inspect SAN domain coverage and certificate fingerprint hashes.
Step 4
Click "Copy Certificate Summary".
Practical Use Cases for SSL Certificate Decoder
SSL Expiration & Domain Coverage Auditing
Verify certificate expiration dates (`Not Before` / `Not After`) and inspect all multi-domain SAN wildcards (`*.example.com`).
Certificate Signing Request (CSR) Verification
Inspect generated CSR files before submitting them to Certificate Authorities (DigiCert, Let's Encrypt, Sectigo) to ensure key length and domain accuracy.
Input & Output Examples
Decoding PEM Certificate
-----BEGIN CERTIFICATE-----\nMIIEkjCCA3qgAwIBAgI...\n-----END CERTIFICATE-----
Subject: CN=renderxd.com | Issuer: Let's Encrypt | Valid: 2026-01-01 to 2026-04-01 | SANs: renderxd.com, *.renderxd.com
Key Features & Performance
- ✓Decodes X.509 PEM certificates, CSRs (PKCS#10), and public keys.
- ✓Extracts Subject CN, SANs, Issuer, Algorithm (RSA 2048/4096, ECC P-256), and Validity dates.
- ✓Live expiration warning countdown badge (Days Remaining).
- ✓100% Client-Side ASN.1 parsing guarantees private key confidentiality.
- ✓1-Click Copy decoded certificate details.
Key Terminology & Definitions
X.509 Standard
The ITU-T standard defining the format of public key certificates, used globally in TLS/SSL web encryption.
Subject Alternative Name (SAN)
An X.509 certificate extension that allows multiple domain names, subdomains, and IP addresses to be protected under a single certificate.