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Windows Program Manager group file (.grp)

.grp file signature | application/octet-stream

Windows 3.xProgram ManagerProgram Group file format

Safe

Magic Bytes

Offset 0
50 4D 43 43

Sources: Wikipedia, Gary Kessler

Extension

.grp

MIME Type

application/octet-stream

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .grp files in Python

Python 
def is_grp(file_path: str) -> bool:
    """Check if file is a valid GRP by magic bytes."""
    signature = bytes([0x50, 0x4D, 0x43, 0x43])
    with open(file_path, "rb") as f:
        return f.read(4) == signature

How to validate .grp files in Node.js

Node.js 
function isGRP(buffer: Buffer): boolean {
  const signature = Buffer.from([0x50, 0x4D, 0x43, 0x43]);
  return buffer.subarray(0, 4).equals(signature);
}

How to validate .grp files in Go

Go 
func IsGRP(data []byte) bool {
    signature := []byte{0x50, 0x4D, 0x43, 0x43}
    if len(data) < 4 {
        return false
    }
    return bytes.Equal(data[:4], signature)
}

API Endpoint

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

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .grp file?

A .grp file is a Windows Program Manager group file file. Windows 3.xProgram ManagerProgram Group file format

What are the magic bytes for .grp files?

The magic bytes for Windows Program Manager group file files are 50 4D 43 43 at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .grp file?

To validate a .grp file, read the first bytes of the file and compare them against the known magic bytes (50 4D 43 43) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .grp files?

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

Is it safe to open .grp files?

Windows Program Manager group file (.grp) 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.