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YouTube Timed Text (.ytt)

.ytt file signature | application/octet-stream

YouTube Timed Text (subtitle) file

Safe

Magic Bytes

Offset 0
EF BB BF 3C 3F 78 6D 6C 20 76 65 72 73 69 6F 6E

Sources: Gary Kessler

Extension

.ytt

MIME Type

application/octet-stream

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .ytt files in Python

Python 
def is_ytt(file_path: str) -> bool:
    """Check if file is a valid YTT by magic bytes."""
    signature = bytes([0xEF, 0xBB, 0xBF, 0x3C, 0x3F, 0x78, 0x6D, 0x6C, 0x20, 0x76, 0x65, 0x72, 0x73, 0x69, 0x6F, 0x6E])
    with open(file_path, "rb") as f:
        return f.read(16) == signature

How to validate .ytt files in Node.js

Node.js 
function isYTT(buffer: Buffer): boolean {
  const signature = Buffer.from([0xEF, 0xBB, 0xBF, 0x3C, 0x3F, 0x78, 0x6D, 0x6C, 0x20, 0x76, 0x65, 0x72, 0x73, 0x69, 0x6F, 0x6E]);
  return buffer.subarray(0, 16).equals(signature);
}

How to validate .ytt files in Go

Go 
func IsYTT(data []byte) bool {
    signature := []byte{0xEF, 0xBB, 0xBF, 0x3C, 0x3F, 0x78, 0x6D, 0x6C, 0x20, 0x76, 0x65, 0x72, 0x73, 0x69, 0x6F, 0x6E}
    if len(data) < 16 {
        return false
    }
    return bytes.Equal(data[:16], signature)
}

API Endpoint

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

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .ytt file?

A .ytt file is a YouTube Timed Text file. YouTube Timed Text (subtitle) file

What are the magic bytes for .ytt files?

The magic bytes for YouTube Timed Text files are EF BB BF 3C 3F 78 6D 6C 20 76 65 72 73 69 6F 6E at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .ytt file?

To validate a .ytt file, read the first bytes of the file and compare them against the known magic bytes (EF BB BF 3C 3F 78 6D 6C 20 76 65 72 73 69 6F 6E) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .ytt files?

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

Is it safe to open .ytt files?

YouTube Timed Text (.ytt) 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.