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UUencoded BASE64 fileTrailer:0A 3D 3D 3D 3D 0A (.b64)

.b64 file signature | application/octet-stream

UUencoded BASE64 fileTrailer:0A 3D 3D 3D 3D 0A(.====.)

Safe

Magic Bytes

Offset 0
62 65 67 69 6E

Sources: Gary Kessler

All Known Signatures

2 signature variants are documented for .b64 files across multiple sources.

Hex Signature Offset Sources
62 65 67 69 6E 0 Gary Kessler
62 65 67 69 6E 2D 62 61 73 65 36 34 0 Gary Kessler

Extension

.b64

MIME Type

application/octet-stream

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .b64 files in Python

Python 
def is_b64(file_path: str) -> bool:
    """Check if file is a valid B64 by magic bytes."""
    signature = bytes([0x62, 0x65, 0x67, 0x69, 0x6E])
    with open(file_path, "rb") as f:
        return f.read(5) == signature

How to validate .b64 files in Node.js

Node.js 
function isB64(buffer: Buffer): boolean {
  const signature = Buffer.from([0x62, 0x65, 0x67, 0x69, 0x6E]);
  return buffer.subarray(0, 5).equals(signature);
}

How to validate .b64 files in Go

Go 
func IsB64(data []byte) bool {
    signature := []byte{0x62, 0x65, 0x67, 0x69, 0x6E}
    if len(data) < 5 {
        return false
    }
    return bytes.Equal(data[:5], signature)
}

API Endpoint

GET /api/v1/b64
curl https://filesignature.org/api/v1/b64

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .b64 file?

A .b64 file is a UUencoded BASE64 fileTrailer:0A 3D 3D 3D 3D 0A file. UUencoded BASE64 fileTrailer:0A 3D 3D 3D 3D 0A(.====.)

What are the magic bytes for .b64 files?

The magic bytes for UUencoded BASE64 fileTrailer:0A 3D 3D 3D 3D 0A files are 62 65 67 69 6E at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .b64 file?

To validate a .b64 file, read the first bytes of the file and compare them against the known magic bytes (62 65 67 69 6E) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .b64 files?

There is no officially registered MIME type for .b64 files. Systems typically use application/octet-stream as a generic fallback when handling this format.

Is it safe to open .b64 files?

UUencoded BASE64 fileTrailer:0A 3D 3D 3D 3D 0A (.b64) 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.