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Windows NT/2000/XP printer spool file (.spl)

.spl file signature | application/octet-stream

Windows NT/2000/XP printer spool file (SPL) is a print job format used by Microsoft Windows operating systems to store data queued for printing. It is used by the Windows print spooler and related printer drivers to manage pending documents, printer jobs, and output processing. The format is primarily a legacy Windows component; files are generally safe, but untrusted spool files should still be handled carefully because they may originate from incomplete or interrupted print jobs.

Safe

Magic Bytes

Offset 0
00 00 01 00

Sources: Gary Kessler

Extension

.spl

MIME Type

application/octet-stream

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .spl files in Python

Python 
def is_spl(file_path: str) -> bool:
    """Check if file is a valid SPL by magic bytes."""
    signature = bytes([0x00, 0x00, 0x01, 0x00])
    with open(file_path, "rb") as f:
        return f.read(4) == signature

How to validate .spl files in Node.js

Node.js 
function isSPL(buffer: Buffer): boolean {
  const signature = Buffer.from([0x00, 0x00, 0x01, 0x00]);
  return buffer.subarray(0, 4).equals(signature);
}

How to validate .spl files in Go

Go 
func IsSPL(data []byte) bool {
    signature := []byte{0x00, 0x00, 0x01, 0x00}
    if len(data) < 4 {
        return false
    }
    return bytes.Equal(data[:4], signature)
}

API Endpoint

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

See the full API documentation for all endpoints and parameters.

Related Formats

.ico

Frequently Asked Questions

What is a .spl file?

A .spl file is a Windows NT/2000/XP printer spool file file. Windows NT/2000/XP printer spool file (SPL) is a print job format used by Microsoft Windows operating systems to store data queued for printing. It is used by the Windows print spooler and related printer drivers to manage pending documents, printer jobs, and output processing. The format is primarily a legacy Windows component; files are generally safe, but untrusted spool files should still be handled carefully because they may originate from incomplete or interrupted print jobs.

What are the magic bytes for .spl files?

The magic bytes for Windows NT/2000/XP printer spool file files are 00 00 01 00 at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .spl file?

To validate a .spl file, read the first bytes of the file and compare them against the known magic bytes (00 00 01 00) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .spl files?

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

Is it safe to open .spl files?

Windows NT/2000/XP printer spool file (.spl) 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.