OpenType font file magic bytes (.otf)
.otf file signature: 4F 54 54 4F 00 | application/x-font-otf
Category: Fonts
OpenType is a digital font format developed by Microsoft and Adobe and maintained as an open standard through the OpenType specification. It is used in operating systems, desktop publishing applications, web browsers, and design software to render scalable text with advanced typographic features and multilingual character support. OpenType fonts are generally safe, though malformed files can trigger parsing bugs in font renderers, so untrusted files should be opened carefully.
Magic Bytes
Offset 0
4F 54 54 4F 00
Sources: Apache Tika, Gary Kessler
All Known Signatures
2 signature variants are documented for .otf files across multiple sources.
| Hex Signature | Offset | Sources |
|---|---|---|
| 4F 54 54 4F 00 | 0 | Apache Tika, Gary Kessler |
| 4F 54 54 4F | 0 | Wikipedia |
Validation Code
How to validate .otf files in Python
def is_otf(file_path: str) -> bool:
"""Check if file is a valid OTF by magic bytes."""
signature = bytes([0x4F, 0x54, 0x54, 0x4F, 0x00])
with open(file_path, "rb") as f:
return f.read(5) == signatureHow to validate .otf files in Node.js
function isOTF(buffer: Buffer): boolean {
const signature = Buffer.from([0x4F, 0x54, 0x54, 0x4F, 0x00]);
return buffer.subarray(0, 5).equals(signature);
}How to validate .otf files in Go
func IsOTF(data []byte) bool {
signature := []byte{0x4F, 0x54, 0x54, 0x4F, 0x00}
if len(data) < 5 {
return false
}
return bytes.Equal(data[:5], signature)
}API Endpoint
/api/v1/otf
curl https://filesignature.org/api/v1/otf
See the full API documentation for all endpoints and parameters.
Related Formats
Frequently Asked Questions
What is a .otf file?
A .otf file is an OpenType font file. OpenType is a digital font format developed by Microsoft and Adobe and maintained as an open standard through the OpenType specification. It is used in operating systems, desktop publishing applications, web browsers, and design software to render scalable text with advanced typographic features and multilingual character support. OpenType fonts are generally safe, though malformed files can trigger parsing bugs in font renderers, so untrusted files should be opened carefully.
What are the magic bytes for .otf files?
The magic bytes for OpenType font file (.otf) files are 4F 54 54 4F 00 at byte offset 0. These bytes identify the file format more reliably than the extension alone.
How do I validate a .otf file?
To validate a .otf file, read the first bytes of the file and compare them against the known magic bytes (4F 54 54 4F 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 .otf files?
The primary MIME type for .otf files is application/x-font-otf.
Is it safe to open .otf files?
OpenType font file (.otf) 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.