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OLE object library magic bytes (.olb)

.olb file signature: 4D 5A | application/octet-stream

OLE Object Library (OLB) is a Microsoft file format used to store type libraries and object definitions for Component Object Model (COM) and OLE automation. It is primarily used by development tools and applications to expose interfaces, constants, and methods for programmatic access and interoperability. The format is a legacy Windows component and is generally safe, though files from untrusted sources should still be handled cautiously.

Safe

Magic Bytes

Offset 0
4D 5A

Sources: Gary Kessler

Extension

.olb

MIME Type

application/octet-stream

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .olb files in Python

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

How to validate .olb files in Node.js

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

How to validate .olb files in Go

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

API Endpoint

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

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .olb file?

A .olb file is an OLE object library. OLE Object Library (OLB) is a Microsoft file format used to store type libraries and object definitions for Component Object Model (COM) and OLE automation. It is primarily used by development tools and applications to expose interfaces, constants, and methods for programmatic access and interoperability. The format is a legacy Windows component and is generally safe, though files from untrusted sources should still be handled cautiously.

What are the magic bytes for .olb files?

The magic bytes for OLE object library (.olb) files are 4D 5A at byte offset 0. These bytes identify the file format more reliably than the extension alone.

How do I validate a .olb file?

To validate a .olb 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 .olb files?

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

Is it safe to open .olb files?

OLE object library (.olb) 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.