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ASCIISTL (.stl)

.stl file signature | application/octet-stream

ASCIISTL (STereoLithography) filefor 3D printing.

Safe

Magic Bytes

Offset 0
73 6F 6C 69 64

Sources: Gary Kessler

Extension

.stl

MIME Type

application/octet-stream

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .stl files in Python

Python 
def is_stl(file_path: str) -> bool:
    """Check if file is a valid STL by magic bytes."""
    signature = bytes([0x73, 0x6F, 0x6C, 0x69, 0x64])
    with open(file_path, "rb") as f:
        return f.read(5) == signature

How to validate .stl files in Node.js

Node.js 
function isSTL(buffer: Buffer): boolean {
  const signature = Buffer.from([0x73, 0x6F, 0x6C, 0x69, 0x64]);
  return buffer.subarray(0, 5).equals(signature);
}

How to validate .stl files in Go

Go 
func IsSTL(data []byte) bool {
    signature := []byte{0x73, 0x6F, 0x6C, 0x69, 0x64}
    if len(data) < 5 {
        return false
    }
    return bytes.Equal(data[:5], signature)
}

API Endpoint

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

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .stl file?

A .stl file is a ASCIISTL file. ASCIISTL (STereoLithography) filefor 3D printing.

What are the magic bytes for .stl files?

The magic bytes for ASCIISTL files are 73 6F 6C 69 64 at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .stl file?

To validate a .stl file, read the first bytes of the file and compare them against the known magic bytes (73 6F 6C 69 64) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .stl files?

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

Is it safe to open .stl files?

ASCIISTL (.stl) 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.