Certificate and key decoders: X.509, CSR, PEM, SSH and ASN.1
Certificate and key decoders parse the DER-encoded ASN.1 structures behind X.509 certificates, certificate signing requests, PEM bundles and SSH or PGP keys, turning them into readable fields such as subject, issuer, validity period, key type and extensions.
Security, PKI & Crypto tools
X.509 Certificate Decoder
Parse a PEM/DER certificate and read its subject, issuer and validity.
CSR Decoder
Decode a Certificate Signing Request and view its subject and key.
PEM / DER / PKCS Decoder
Split and inspect PEM, DER, PKCS#7 and PKCS#12 certificate bundles.
SPIFFE Certificate Decoder
Extract SPIFFE IDs and SVIDs from workload certificates.
SSH Key Decoder
Decode SSH public and private key blobs and read their fields.
PGP / GPG Armored Decoder
De-armor PGP keys and messages and inspect their packets.
ASN.1 & OID Decoder
Walk an ASN.1 DER structure and resolve object identifiers.
LDAP / Kerberos Ticket Decoder
Decode Kerberos tickets and LDAP structures.
NTLM Auth Header Decoder
Parse NTLM type 1/2/3 authentication messages.
Which decoder do I need?
- A -----BEGIN CERTIFICATE----- block
- X.509 Certificate
- A -----BEGIN CERTIFICATE REQUEST----- block
- CSR
- An ssh-ed25519 or ssh-rsa public key line
- SSH Key
- Raw DER bytes you need to walk tag by tag
- ASN.1 & OID
About security, pki & crypto decoding
Almost every artefact in public-key infrastructure is ASN.1 encoded with DER and, more often than not, wrapped in a PEM envelope — the familiar -----BEGIN CERTIFICATE----- block. Reading one normally means reaching for openssl x509 -text or openssl req -text; a browser-based decoder gives the same field-by-field view without a terminal.
The decoders in this category are on the roadmap: each page already carries a reference explainer, a spec table and an FAQ for the format, and the interactive parsers will ship here as they are finished. Until then, the Base64 and hex decoders are useful for a first look at a DER blob.
Frequently asked questions
What is the difference between PEM and DER?
DER is the binary ASN.1 encoding of a certificate or key. PEM is that same DER data Base64-encoded and wrapped in -----BEGIN ...----- and -----END ...----- lines so it can be pasted as text.
Is a certificate secret?
No. Certificates and public keys are designed to be shared. Private keys are the secret part — never paste a private key into a tool that sends data to a server.
Last reviewed · found a mistake? contact@decoder.tools