ASN.1 DecoderDecode ASN.1 DER/BER structures from PEM, Base64, or hex.
ASN.1 Decoder
Decode ASN.1 DER/BER structures from PEM, Base64, or hex.
Paste
PEM/Base64/hex ASN.1 data.
Decode
Parse structure.
Inspect
View TLV tree.
What Is ASN.1 Decoder?
Decodes ASN.1 DER/BER binary structures displaying tag-length-value tree. Recognizes SEQUENCE, SET, INTEGER, BIT STRING, OCTET STRING, OID, and string types. Accepts PEM, Base64, or hex input. Essential for X.509 certificates and PKCS keys. All client-side.
Why Use Our ASN.1 Decoder?
- PEM/Base64/hex input
- Common ASN.1 types
- Hierarchical display
- 100% client-side
Common Use Cases
Certificates
X.509 structure.
Keys
PKCS structures.
Protocols
ASN.1 messages.
Education
Encoding rules.
Technical Guide
TLV parsing: 0x02=INTEGER, 0x30=SEQUENCE, 0x06=OID, etc. Constructed types (bit 5) parsed recursively to depth 10. Length: short (0-127), long (0x80|n).
Tips & Best Practices
- 1Works with X.509, PKCS
- 2PEM headers stripped
- 3Recursive parsing
- 4Values truncated
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Encoding & CryptoFrequently Asked Questions
QFree?
QInput?
QCertificates?
QSafe?
QTypes?
About ASN.1 Decoder
ASN.1 Decoder is a free online tool from FreeToolkit.ai. All processing happens directly in your browser โ your data never leaves your device. No registration required. No ads. Just fast, reliable tools.