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Pure python implementation of magic file detection

Project description

puremagic is a pure python module that will identify a file based off it’s magic numbers.

CoverageStatus License PyPi

It is designed to be minimalistic and inherently cross platform compatible. It is also designed to be a stand in for python-magic, it incorporates the functions from_file(filename[, mime]) and from_string(string[, mime]) however the magic_file() and magic_string() are more powerful and will also display confidence and duplicate matches.

It does NOT try to match files off non-magic string. In other words it will not search for a string within a certain window of bytes like others might.

Advantages over using a wrapper for ‘file’ or ‘libmagic’:

  • Faster

  • Lightweight

  • Cross platform compatible

  • No dependencies


  • Does not have as many file types

  • No multilingual comments

  • Duplications due to small or reused magic numbers

(Help fix the first two disadvantages by contributing!)


  • Python 3.8+

Using github ci to run continuous integration tests on listed platforms.

Install from pypy

$ pip install puremagic

On linux environments, you may want to be clear you are using python3

$ python3 -m pip install puremagic

Install from source

In either a virtualenv or globally, simply run:

$ python install


“from_file” will return the most likely file extension. “magic_file” will give you every possible result it finds, as well as the confidence.

import puremagic

filename = "test/resources/images/test.gif"

ext = puremagic.from_file(filename)
# '.gif'

# [['.gif', 'image/gif', 'Graphics interchange format file (GIF87a)', 0.7],
#  ['.gif', '', 'GIF file', 0.5]]

With “magic_file” it gives each match, highest confidence first:

  • possible extension(s)

  • mime type

  • description

  • confidence (All headers have to perfectly match to make the list, however this orders it by longest header, therefore most precise, first)

If you already have a file open, or raw byte string, you could also use:

  • from_string

  • from_stream

  • magic_string

  • magic_stream

with open(r"test\resources\video\test.mp4", "rb") as file:

# [PureMagicWithConfidence(byte_match=b'ftypisom', offset=4, extension='.mp4', mime_type='video/mp4', name='MPEG-4 video', confidence=0.8),
#  PureMagicWithConfidence(byte_match=b'iso2avc1mp4', offset=20, extension='.mp4', mime_type='video/mp4', name='MP4 Video', confidence=0.8)]



$ python -m puremagic [options] filename <filename2>...


$ python -m puremagic test/resources/images/test.gif
'test/resources/images/test.gif' : .gif

$ python -m puremagic -m test/resources/images/test.gif test/resources/audio/test.mp3
'test/resources/images/test.gif' : image/gif
'test/resources/audio/test.mp3' : audio/mpeg

imghdr replacement

If you are looking for a replacement for the standard library’s depreciated imghdr, you can use puremagic.what()

import puremagic

filename = "test/resources/images/test.gif"

ext = puremagic.what(filename)
# 'gif'


The file type is actually X but it’s showing up as Y with higher confidence?

This can happen when the file’s signature happens to match a subset of a file standard. The subset signature will be longer, therefore report with greater confidence, because it will have both the base file type signature plus the additional subset one.

You don’t have sliding offsets that could better detect plenty of common formats, why’s that?

Design choice, so it will be a lot faster and more accurate. Without more intelligent or deeper identification past a sliding offset I don’t feel comfortable including it as part of a ‘magic number’ library.

Your version isn’t as complete as I want it to be, where else should I look?

Look into python modules that wrap around libmagic or use something like Apache Tika.


Gary C. Kessler

For use of his File Signature Tables, available at:

For use of their shared-mime-info file (even if they do use XML, blea), available at:


MIT Licenced, see LICENSE, Copyright (c) 2013-2024 Chris Griffith

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