der
What is a .der file?
application/x-x509-ca-cert
DER (Distinguished Encoding Rules) is the binary encoding of an X.509 certificate (or other ASN.1 structure) — the same data a PEM file Base64-wraps, without the text armour. A .der certificate is compact and byte-exact, common in Java keystores and Windows tooling.
How to use a .der file
Use an example .der certificate to test binary X.509 parsers, ASN.1 decoders, and DER-to-PEM converters, or to confirm a tool reads raw certificate bytes. Published sample certificate, not a real identity.