ToolZeno

PEM Viewer & Certificate Decoder

Inspect and decode PEM-encoded files (X.509 Certificates, Certificate Chains, CSRs, RSA & EC Keys) locally in your browser. All parsing is performed 100% client-side for maximum security.

100% Client-Side Private Inspection: All PEM decoding, ASN.1 parsing, and fingerprint calculations occur locally inside your browser. No files or certificates are ever uploaded to any server.

Step 1: Load PEM Data

Upload a certificate file or paste PEM contents. All processing happens 100% locally in your browser.

550 characters
Quick Sample Presets:

Complete Guide to PEM Files and X.509 Certificate Inspection

The Toolzeno PEM Viewer provides a secure, client-side online decoder to inspect X.509 certificates, certificate chains, CSRs, RSA keys, EC keys, and public keys directly in your browser. Whether you are debugging SSL/TLS configuration issues, checking certificate expiration dates, verifying Subject Alternative Names (SAN), or auditing PKI credentials, this tool parses ASN.1 structures instantly without transmitting private data to any remote server.

Common PEM Block Types

  • X.509 Certificate: -----BEGIN CERTIFICATE-----
  • Certificate Request (CSR): -----BEGIN CERTIFICATE REQUEST-----
  • RSA Private Key: -----BEGIN RSA PRIVATE KEY-----
  • PKCS#8 Private Key: -----BEGIN PRIVATE KEY-----
  • EC Private Key: -----BEGIN EC PRIVATE KEY-----
  • Public Key: -----BEGIN PUBLIC KEY-----

PEM vs DER Comparison

Cryptographic objects are natively encoded using ASN.1 DER binary format. Because binary data cannot be safely pasted into configuration files, email, or web forms, PEM wraps DER binary payloads in Base64 ASCII text with distinctive header and footer delimiters.

Information Extracted by PEM Viewer

Subject & Issuer RDNsCommon Name (CN), Organization (O), Organizational Unit (OU), Country (C), State (ST), Locality (L), Email.
Validity & ExpirationNotBefore date, NotAfter date, UTC/Local formatting, relative expiration countdown, validity status badges.
Fingerprints & SerialSHA-1 and SHA-256 binary hash fingerprints, formatted Hex serial number, Decimal serial representation.
X.509 v3 ExtensionsKey Usage, Extended Key Usage (EKU), Subject Alternative Name (SAN), Basic Constraints (Is CA), AKI/SKI.
Public Key SpecificationsAlgorithm (RSA, EC, Ed25519), bit length (2048, 4096), elliptic curve name (secp256r1, P-384, P-521).
100% Client-Side PrivacyZero network calls, zero data uploads, local Web Crypto API parsing, complete security guarantee.

Frequently Asked Questions

PEM (Privacy-Enhanced Mail) is a container format commonly used to store and transmit cryptographic certificates, private keys, certificate signing requests (CSRs), and certificate chains. A PEM file contains Base64-encoded ASCII text delimited by header and footer markers such as -----BEGIN CERTIFICATE----- and -----END CERTIFICATE-----.

No. 100% of the decoding and inspection is performed client-side locally in your web browser using Web Crypto APIs and JavaScript ASN.1 parsing. Your certificate data, private keys, and file contents are never transmitted across the network, stored, or logged.

DER (Distinguished Encoding Rules) is a binary representation of ASN.1 encoded cryptographic data. PEM is simply the Base64 ASCII text wrapper around the raw binary DER data with readable -----BEGIN ...----- and -----END ...----- headers and footers.

Yes! The PEM Viewer automatically detects encrypted private key blocks (such as PKCS#8 or OpenSSL encrypted keys) and displays header metadata, key format, and block parameters. Since processing is strictly read-only, key decryption requiring passwords is not attempted.

When you paste or upload a file containing multiple PEM blocks (such as Server, Intermediate, and Root CA certificates), Toolzeno automatically parses all blocks and displays a tab bar letting you inspect each individual certificate in the chain.

Related Tools

Hash Generator

Compute MD5, SHA-1, SHA-256, and SHA-512 cryptographic checksums in-browser.

Open Tool

HMAC Generator

Generate Keyed-Hash Message Authentication Codes (HMAC) client-side for secure API authentication.

Open Tool

JWT Decoder

Decode JSON Web Tokens, parse payloads, and inspect cryptographic signatures client-side.

Open Tool

Secret Key Generator

Generate cryptographically secure secret keys, API tokens, JWT secrets, AES-256 keys, and HMAC signatures 100% client-side using Web Crypto API.

Open Tool