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MicrosoftCommon Object File Format (.obj)

.obj file signature | application/octet-stream

Microsoft Common Object File Format (COFF) is a relocatable object file format developed and maintained by Microsoft for use on Intel 386 and compatible systems. It is used to store compiled code and symbols during linking, and appears in software development toolchains for Windows and related environments. The format is largely historical, having been superseded in many workflows by newer executable and object formats; files are generally low risk when handled by standard tools.

Safe

Magic Bytes

Offset 0
4C 01

Sources: Gary Kessler

Extension

.obj

MIME Type

application/octet-stream

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .obj files in Python

Python 
def is_obj(file_path: str) -> bool:
    """Check if file is a valid OBJ by magic bytes."""
    signature = bytes([0x4C, 0x01])
    with open(file_path, "rb") as f:
        return f.read(2) == signature

How to validate .obj files in Node.js

Node.js 
function isOBJ(buffer: Buffer): boolean {
  const signature = Buffer.from([0x4C, 0x01]);
  return buffer.subarray(0, 2).equals(signature);
}

How to validate .obj files in Go

Go 
func IsOBJ(data []byte) bool {
    signature := []byte{0x4C, 0x01}
    if len(data) < 2 {
        return false
    }
    return bytes.Equal(data[:2], signature)
}

API Endpoint

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

See the full API documentation for all endpoints and parameters.

Related Formats

.3ds .blend .glb .stl

Frequently Asked Questions

What is a .obj file?

A .obj file is a MicrosoftCommon Object File Format file. Microsoft Common Object File Format (COFF) is a relocatable object file format developed and maintained by Microsoft for use on Intel 386 and compatible systems. It is used to store compiled code and symbols during linking, and appears in software development toolchains for Windows and related environments. The format is largely historical, having been superseded in many workflows by newer executable and object formats; files are generally low risk when handled by standard tools.

What are the magic bytes for .obj files?

The magic bytes for MicrosoftCommon Object File Format files are 4C 01 at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .obj file?

To validate a .obj file, read the first bytes of the file and compare them against the known magic bytes (4C 01) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .obj files?

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

Is it safe to open .obj files?

MicrosoftCommon Object File Format (.obj) 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.