MicrosoftCommon Object File Format (.obj)

.obj file signature | application/octet-stream

MicrosoftCommon Object File Format (COFF)relocatableobject code file for an Intel 386 or later/compatible processors

Safe

Magic Bytes

Offset 0


              4C 01

Sources: Gary Kessler

All Known Signatures

2 signature variants are documented for .obj files across multiple sources.

Hex Signature	Offset	Sources
4C 01	0	Gary Kessler
7F 45 4C 46	0	Gary Kessler

Extension

.obj

MIME Type

application/octet-stream

Byte Offset

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

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.

Frequently Asked Questions

What is a .obj file?

A .obj file is a MicrosoftCommon Object File Format file. MicrosoftCommon Object File Format (COFF)relocatableobject code file for an Intel 386 or later/compatible processors

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.