Max image size on file upload

Solution 1:

models.py

class Product(models.Model):
    image = models.ImageField(upload_to="/a/b/c/")

forms.py

class ProductForm(forms.ModelForm):
    # Add some custom validation to our image field
    def clean_image(self):
        image = self.cleaned_data.get('image', False)
        if image:
            if image._size > 4*1024*1024:
                raise ValidationError("Image file too large ( > 4mb )")
            return image
        else:
            raise ValidationError("Couldn't read uploaded image")

Solution 2:

Essentially this is a duplicate of Django File upload size limit

You have two options:

1. Use validation in Django to check the uploaded file's size. The problem with this approach is that the file must be uploaded completely before it is validated. This means that if someone uploads a 1TB file, you'll probably run out of hard drive space before the user gets a form error.

2. Configure the Web server to limit the allowed upload body size. e.g. if using Apache, set the LimitRequestBody setting. This will mean if a user tries to upload too much, they'll get an error page configurable in Apache

As @pastylegs says in the comments, using a combination of both is probably the best approach. Say you want a maximum of 5MB, perhaps enforce a 20MB limit at the Web server level, and the 5MB limit at the Django level. The 20MB limit would provide some protection against malicious users, while the 5MB limit in Django provides good UX.