ASN.1 / DER Structure Parser
Decode DER hex or PEM into a readable ASN.1 tree.
Free · no sign-up · runs locally·
About this tool
Every certificate, key, and CSR is an ASN.1 structure serialized as DER. This parser walks the raw bytes and renders the tag tree — SEQUENCEs, OBJECT IDENTIFIERs (with well-known names), INTEGERs, UTF8Strings, and timestamps — so you can see exactly what a blob contains.
Paste DER as hex or a full PEM block; parsing is done byte-by-byte in your browser.
Like everything on encrypt.tools, this runs entirely in your browser — nothing you enter is transmitted or stored.
Do the same in a terminal
Reproduce or cross-check this tool with standard command-line utilities. For deterministic operations like hashing and encoding, the output matches exactly.
openssl asn1parse -in cert.pem -iFrequently asked questions about ASN.1 Parser
What is ASN.1 and DER?+
ASN.1 is a notation for structured data; DER is its binary encoding. Certificates, keys, and CSRs are all ASN.1 structures serialized as DER, then often Base64-wrapped as PEM.
What can I paste here?+
A PEM block or raw DER as hex. The parser walks the byte structure and shows the tag tree with common OIDs named.
Is it safe to parse a private key?+
Parsing runs entirely in your browser, so nothing is uploaded. Still, only handle private keys on machines you trust.