Only accept a certain file type in FileField, server-side

Question

How can I restrict FileField to only accept a certain type of file (video, audio, pdf, etc.) in an elegant way, server-side?

Answer 1

Django in version 1.11 has a newly added FileExtensionValidator for model fields, the docs is here: https://docs.djangoproject.com/en/dev/ref/validators/#fileextensionvalidator.

An example of how to validate a file extension:

from django.core.validators import FileExtensionValidator
from django.db import models

class MyModel(models.Model):
    pdf_file = models.FileField(upload_to='foo/',
                                validators=[FileExtensionValidator(allowed_extensions=['pdf'])])

Note that this method is not safe. Citation from Django docs:

Don’t rely on validation of the file extension to determine a file’s type. Files can be renamed to have any extension no matter what data they contain.

There is also new validate_image_file_extension (https://docs.djangoproject.com/en/dev/ref/validators/#validate-image-file-extension) for validating image extensions (using Pillow).