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DER (.der)

.der file signature | application/x-x509-cert;format=der

Safe

Magic Bytes

Offset 0
30 80

Sources: Apache Tika

Extension

.der

MIME Type

application/x-x509-cert;format=der

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .der files in Python

Python 
def is_der(file_path: str) -> bool:
    """Check if file is a valid DER by magic bytes."""
    signature = bytes([0x30, 0x80])
    with open(file_path, "rb") as f:
        return f.read(2) == signature

How to validate .der files in Node.js

Node.js 
function isDER(buffer: Buffer): boolean {
  const signature = Buffer.from([0x30, 0x80]);
  return buffer.subarray(0, 2).equals(signature);
}

How to validate .der files in Go

Go 
func IsDER(data []byte) bool {
    signature := []byte{0x30, 0x80}
    if len(data) < 2 {
        return false
    }
    return bytes.Equal(data[:2], signature)
}

API Endpoint

GET /api/v1/der
curl https://filesignature.org/api/v1/der

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .der file?

A .der file is a DER file.

What are the magic bytes for .der files?

The magic bytes for DER files are 30 80 at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .der file?

To validate a .der file, read the first bytes of the file and compare them against the known magic bytes (30 80) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .der files?

The primary MIME type for .der files is application/x-x509-cert;format=der.

Is it safe to open .der files?

DER (.der) files are generally safe to open. They are classified as low risk because they primarily contain data rather than executable code. However, always ensure files come from a trusted source.