Commodore 1541 GCR-encoded disk image (.g64)
.g64 file signature | application/octet-stream
G64 is a GCR-encoded disk image format for the Commodore 1541 floppy disk drive, originally defined for Commodore 64 software preservation and maintained by the retrocomputing community. It is used to archive, transfer, and emulate copy-protected and track-sensitive disk data in C64 emulators and preservation tools. The format is legacy and largely obsolete, and files are generally safe to open with compatible software.
Magic Bytes
Offset 0
47 43 52 2D 31 35 34 31
Sources: Schepers C64 Format Spec
All Known Signatures
2 signature variants are documented for .g64 files across multiple sources.
| Hex Signature | Offset | Sources |
|---|---|---|
| 47 43 52 2D 31 35 34 31 | 0 | Schepers C64 Format Spec |
| 47 65 6E 65 74 65 63 20 4F 6D 6E 69 63 61 73 74 | 0 | Gary Kessler |
Extension
.g64
MIME Type
application/octet-stream
Byte Offset
0
Risk Level
Safe
Validation Code
How to validate .g64 files in Python
def is_g64(file_path: str) -> bool:
"""Check if file is a valid G64 by magic bytes."""
signature = bytes([0x47, 0x43, 0x52, 0x2D, 0x31, 0x35, 0x34, 0x31])
with open(file_path, "rb") as f:
return f.read(8) == signatureHow to validate .g64 files in Node.js
function isG64(buffer: Buffer): boolean {
const signature = Buffer.from([0x47, 0x43, 0x52, 0x2D, 0x31, 0x35, 0x34, 0x31]);
return buffer.subarray(0, 8).equals(signature);
}How to validate .g64 files in Go
func IsG64(data []byte) bool {
signature := []byte{0x47, 0x43, 0x52, 0x2D, 0x31, 0x35, 0x34, 0x31}
if len(data) < 8 {
return false
}
return bytes.Equal(data[:8], signature)
}API Endpoint
/api/v1/g64
curl https://filesignature.org/api/v1/g64
See the full API documentation for all endpoints and parameters.
Frequently Asked Questions
What is a .g64 file?
A .g64 file is a Commodore 1541 GCR-encoded disk image file. G64 is a GCR-encoded disk image format for the Commodore 1541 floppy disk drive, originally defined for Commodore 64 software preservation and maintained by the retrocomputing community. It is used to archive, transfer, and emulate copy-protected and track-sensitive disk data in C64 emulators and preservation tools. The format is legacy and largely obsolete, and files are generally safe to open with compatible software.
What are the magic bytes for .g64 files?
The magic bytes for Commodore 1541 GCR-encoded disk image files are 47 43 52 2D 31 35 34 31 at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.
How do I validate a .g64 file?
To validate a .g64 file, read the first bytes of the file and compare them against the known magic bytes (47 43 52 2D 31 35 34 31) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.
What is the MIME type for .g64 files?
There is no officially registered MIME type for .g64 files. Systems typically use application/octet-stream as a generic fallback when handling this format.
Is it safe to open .g64 files?
Commodore 1541 GCR-encoded disk image (.g64) 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.