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ActiveX or OLE Custom Control (.ocx)

.ocx file signature | application/octet-stream

ActiveX or OLE Custom Control (OCX) is a Microsoft-developed Windows component format maintained within the ActiveX and COM ecosystem. It is used to distribute reusable controls for applications such as Visual Basic programs, legacy business software, and other Windows desktop interfaces. Because OCX files can contain executable code and are a legacy technology, they should be obtained only from trusted sources and used with caution.

Safe

Magic Bytes

Offset 0
4D 5A

Sources: Wikipedia, Gary Kessler

Extension

.ocx

MIME Type

application/octet-stream

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .ocx files in Python

Python 
def is_ocx(file_path: str) -> bool:
    """Check if file is a valid OCX by magic bytes."""
    signature = bytes([0x4D, 0x5A])
    with open(file_path, "rb") as f:
        return f.read(2) == signature

How to validate .ocx files in Node.js

Node.js 
function isOCX(buffer: Buffer): boolean {
  const signature = Buffer.from([0x4D, 0x5A]);
  return buffer.subarray(0, 2).equals(signature);
}

How to validate .ocx files in Go

Go 
func IsOCX(data []byte) bool {
    signature := []byte{0x4D, 0x5A}
    if len(data) < 2 {
        return false
    }
    return bytes.Equal(data[:2], signature)
}

API Endpoint

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

See the full API documentation for all endpoints and parameters.

Related Formats

.cpl .com .dll .exe .scr .sys

Frequently Asked Questions

What is a .ocx file?

A .ocx file is a ActiveX or OLE Custom Control file. ActiveX or OLE Custom Control (OCX) is a Microsoft-developed Windows component format maintained within the ActiveX and COM ecosystem. It is used to distribute reusable controls for applications such as Visual Basic programs, legacy business software, and other Windows desktop interfaces. Because OCX files can contain executable code and are a legacy technology, they should be obtained only from trusted sources and used with caution.

What are the magic bytes for .ocx files?

The magic bytes for ActiveX or OLE Custom Control files are 4D 5A at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .ocx file?

To validate a .ocx file, read the first bytes of the file and compare them against the known magic bytes (4D 5A) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .ocx files?

There is no officially registered MIME type for .ocx files. Systems typically use application/octet-stream as a generic fallback when handling this format.

Is it safe to open .ocx files?

ActiveX or OLE Custom Control (.ocx) 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.