# ISO Base Media file (MPEG-4) — file signature 66 74 79 70 69 73 6F 6D at offset 4

For ISO Base Media file (MPEG-4), hex signature is 66 74 79 70 69 73 6F 6D; extension is mp4, verified against its source on 2026-09-22.

- **Hex signature:** 66 74 79 70 69 73 6F 6D _(verified: appears in the quote below)_
- **Offset:** 4 _(verified: appears in the quote below)_
- **Extension:** mp4 _(verified: appears in the quote below)_
- **Format:** ISO Base Media file (MPEG-4) _(verified: appears in the quote below)_

## What the source says

> 66 74 79 70 69 73 6F 6D | ftypisom | 4 | mp4 | ISO Base Media file (MPEG-4) |

## Source

- https://en.wikipedia.org/wiki/List_of_file_signatures

Last verified: 2026-09-22. Review by: 2027-09-22.
Part of [File format magic numbers](https://referencesource.org/file-format-signatures/).