Adobe Portable Document Format (.fdf)
.fdf file signature | application/vnd.fdf
Forms Data Format (FDF) is a file format developed by Adobe for exchanging form data, annotations, and related information with PDF documents. It is used primarily with PDF forms, document review workflows, and data submission in Adobe Acrobat and compatible applications. FDF files are generally low risk, but they may reference external content or contain scripted actions, so files from untrusted sources should be opened with standard caution.
Magic Bytes
Offset 0
25 46 44 46 2D
Sources: Apache Tika
All Known Signatures
2 signature variants are documented for .fdf files across multiple sources.
| Hex Signature | Offset | Sources |
|---|---|---|
| 25 46 44 46 2D | 0 | Apache Tika |
| 25 50 44 46 | 0 | Gary Kessler |
Extension
.fdf
MIME Type
application/vnd.fdf
Byte Offset
0
Risk Level
Safe
Validation Code
How to validate .fdf files in Python
def is_fdf(file_path: str) -> bool:
"""Check if file is a valid FDF by magic bytes."""
signature = bytes([0x25, 0x46, 0x44, 0x46, 0x2D])
with open(file_path, "rb") as f:
return f.read(5) == signatureHow to validate .fdf files in Node.js
function isFDF(buffer: Buffer): boolean {
const signature = Buffer.from([0x25, 0x46, 0x44, 0x46, 0x2D]);
return buffer.subarray(0, 5).equals(signature);
}How to validate .fdf files in Go
func IsFDF(data []byte) bool {
signature := []byte{0x25, 0x46, 0x44, 0x46, 0x2D}
if len(data) < 5 {
return false
}
return bytes.Equal(data[:5], signature)
}API Endpoint
/api/v1/fdf
curl https://filesignature.org/api/v1/fdf
See the full API documentation for all endpoints and parameters.
Related Formats
Frequently Asked Questions
What is a .fdf file?
A .fdf file is a Adobe Portable Document Format file. Forms Data Format (FDF) is a file format developed by Adobe for exchanging form data, annotations, and related information with PDF documents. It is used primarily with PDF forms, document review workflows, and data submission in Adobe Acrobat and compatible applications. FDF files are generally low risk, but they may reference external content or contain scripted actions, so files from untrusted sources should be opened with standard caution.
What are the magic bytes for .fdf files?
The magic bytes for Adobe Portable Document Format files are 25 46 44 46 2D at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.
How do I validate a .fdf file?
To validate a .fdf file, read the first bytes of the file and compare them against the known magic bytes (25 46 44 46 2D) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.
What is the MIME type for .fdf files?
The primary MIME type for .fdf files is application/vnd.fdf.
Is it safe to open .fdf files?
Adobe Portable Document Format (.fdf) 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.