To check if a file starts with MZ or GIF, just use file/libmagic.
You don't need AI or Magika for that.
TrID has a lot of heuristics, but a lot of false positives.

Magika is useful in different ways, across binary and source types, and is quite fast. But not fit for weird files.

Magika is a fast file type identifier that covers many file types, binary formats or source texts.
It's not made to detect adversarial attacks.
It's useful for different things that classic binary scanning can't do at this speed.

Magika was trained on all file types with enough available samples.

Weird files are out of scope of Magika. It just wasn't trained on them.

It's trivial to inject some data in a file and keep it functional (w/ my tool Mitra, for example).
So take a JPG, inject a lot of JavaScript data, and ...guess what ?

Check it out: github.com/corkami/mitra

Of course, it's possible to create weird files that will fool Magika and other tools.
Polymocks, polyglots...

I made quite a few - check my CCC talk last year:
speakerdeck.com/ange/fearsom...

Magika uses the first and last kilobytes of the files.
That way, if the file is slightly corrupted, the filetype might still be properly identified.
Magika returns several file types if needed.
It's one of its advantages, but a double-edged sword.

So file contents are used to determine the file type.
To check if the file starts with '\x7FELF', 'MZ' or 'GIF', you don't need IA.

But some file formats don't start with a clear 'magic' signature at offset zero.
And what if you also want to tell apart C++, RUST and HTML ?
No magic for source files

To identify file types, the worst way are file extensions:
the extension is stored in the filesystem entry, not in the file content.
It can be lost, modified, variable...

Almost all file formats are known under several file extensions:
.JPG/.JPEG, .ZIP/.APK/.DOCX, .EXE/.DLL, .ELF/.SO ...

In the process, I also studied in depth other file type identifiers, and I've been contributing to most of them before, including LibMagic, TrID...
Check my talk: speakerdeck.com/ange/overvie...

I love the little details:
Drop and run, piezo sound…

Public blog post:
opensource.googleblog.com/2025/11/anno...

Source: github.com/google/magika

You can do that with my Mitra tool with the `--force` parameter (for arbitrary content injection) on ~40 standard formats (which covers many more subformats).
github.com/corkami/mitra