Developer Studio File Workspace Options subheader magic bytes (.opt)
.opt file signature: D0 CF 11 E0 A1 B1 1A E1 | application/octet-stream
Developer Studio File Workspace Options subheader (OPT) is a legacy Microsoft file format used within Microsoft Developer Studio to store workspace configuration data. It supports development environments by preserving project settings, user preferences, and build options so the IDE can restore a developer’s workspace across sessions. The format is generally considered safe, though it is associated with older Visual Studio-era tooling and is rarely encountered outside legacy projects and archived development files.
Magic Bytes
Offset 0
D0 CF 11 E0 A1 B1 1A E1
Sources: Gary Kessler
All Known Signatures
2 signature variants are documented for .opt files across multiple sources.
| Hex Signature | Offset | Sources |
|---|---|---|
| D0 CF 11 E0 A1 B1 1A E1 | 0 | Gary Kessler |
| FD FF FF FF 20 00 00 00 | 512 | Gary Kessler |
Validation Code
How to validate .opt files in Python
def is_opt(file_path: str) -> bool:
"""Check if file is a valid OPT by magic bytes."""
signature = bytes([0xD0, 0xCF, 0x11, 0xE0, 0xA1, 0xB1, 0x1A, 0xE1])
with open(file_path, "rb") as f:
return f.read(8) == signatureHow to validate .opt files in Node.js
function isOPT(buffer: Buffer): boolean {
const signature = Buffer.from([0xD0, 0xCF, 0x11, 0xE0, 0xA1, 0xB1, 0x1A, 0xE1]);
return buffer.subarray(0, 8).equals(signature);
}How to validate .opt files in Go
func IsOPT(data []byte) bool {
signature := []byte{0xD0, 0xCF, 0x11, 0xE0, 0xA1, 0xB1, 0x1A, 0xE1}
if len(data) < 8 {
return false
}
return bytes.Equal(data[:8], signature)
}API Endpoint
/api/v1/opt
curl https://filesignature.org/api/v1/opt
See the full API documentation for all endpoints and parameters.
Related Formats
Frequently Asked Questions
What is a .opt file?
A .opt file is a Developer Studio File Workspace Options subheader file. Developer Studio File Workspace Options subheader (OPT) is a legacy Microsoft file format used within Microsoft Developer Studio to store workspace configuration data. It supports development environments by preserving project settings, user preferences, and build options so the IDE can restore a developer’s workspace across sessions. The format is generally considered safe, though it is associated with older Visual Studio-era tooling and is rarely encountered outside legacy projects and archived development files.
What are the magic bytes for .opt files?
The magic bytes for Developer Studio File Workspace Options subheader (.opt) files are D0 CF 11 E0 A1 B1 1A E1 at byte offset 0. These bytes identify the file format more reliably than the extension alone.
How do I validate a .opt file?
To validate a .opt file, read the first bytes of the file and compare them against the known magic bytes (D0 CF 11 E0 A1 B1 1A E1) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.
What is the MIME type for .opt files?
There is no officially registered MIME type for .opt files. Systems typically use application/octet-stream as a generic fallback when handling this format.
Is it safe to open .opt files?
Developer Studio File Workspace Options subheader (.opt) 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.