ISO Base Media file (.mp4)

.mp4 file signature | video/mp4

ISO Base Media file (MPEG-4) v1

Safe

Magic Bytes

Offset 4


              66 74 79 70 69 73 6F 6D

Sources: Wikipedia, Gary Kessler

All Known Signatures

6 signature variants are documented for .mp4 files across multiple sources.

Hex Signature	Offset	Sources
66 74 79 70 69 73 6F 6D	4	Wikipedia, Gary Kessler
66 74 79 70 4D 53 4E 56	4	Wikipedia, Gary Kessler
66 74 79 70 6D 70 34 31	4	Apache Tika
66 74 79 70 6D 70 34 32	4	Apache Tika
6D 70 34 32	0	Neil Harvey FileSignatures
69 73 6F 6D	0	Neil Harvey FileSignatures

Extension

.mp4

MIME Type

video/mp4

Byte Offset

Risk Level

Safe

Validation Code

How to validate .mp4 files in Python

Python

def is_mp4(file_path: str) -> bool:
    """Check if file is a valid MP4 by magic bytes."""
    signature = bytes([0x66, 0x74, 0x79, 0x70, 0x69, 0x73, 0x6F, 0x6D])
    with open(file_path, "rb") as f:
        return f.read(8) == signature

How to validate .mp4 files in Node.js

Node.js

function isMP4(buffer: Buffer): boolean {
  const signature = Buffer.from([0x66, 0x74, 0x79, 0x70, 0x69, 0x73, 0x6F, 0x6D]);
  return buffer.subarray(0, 8).equals(signature);
}

How to validate .mp4 files in Go

func IsMP4(data []byte) bool {
    signature := []byte{0x66, 0x74, 0x79, 0x70, 0x69, 0x73, 0x6F, 0x6D}
    if len(data) < 8 {
        return false
    }
    return bytes.Equal(data[:8], signature)
}

API Endpoint

GET /api/v1/mp4


              curl https://filesignature.org/api/v1/mp4

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .mp4 file?

A .mp4 file is a ISO Base Media file file. ISO Base Media file (MPEG-4) v1

What are the magic bytes for .mp4 files?

The magic bytes for ISO Base Media file files are 66 74 79 70 69 73 6F 6D at byte offset 4. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .mp4 file?

To validate a .mp4 file, read the first bytes of the file and compare them against the known magic bytes (66 74 79 70 69 73 6F 6D) at offset 4. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .mp4 files?

The primary MIME type for .mp4 files is video/mp4.

Is it safe to open .mp4 files?

ISO Base Media file (.mp4) 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.