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Add MaxFileSizeValidator and MinFileSizeValidator for file size constraints #9738

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mahdirahimi1999
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@mahdirahimi1999 mahdirahimi1999 commented Jul 12, 2025 •
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Add file size validators for FileField and ImageField

Adds two new validators to enforce file size constraints on uploaded files:

Background

In many of our DRF and Django projects, we work extensively with FileField and ImageField and need to validate file sizes. I've been creating these validators locally, and other developers have been implementing similar solutions. I thought it would be beneficial to create a standardized class that can be added to DRF and used across our projects.

New Validators

  • MaxFileSizeValidator: Ensures files don't exceed a maximum size (in bytes)
  • MinFileSizeValidator: Ensures files meet a minimum size (in bytes)

Features

  • Customizable error messages and codes
  • Deconstructible for migrations
  • Works with FileField and ImageField
  • Gracefully handles objects without .size attribute

Usage

from rest_framework.validators import MaxFileSizeValidator, MinFileSizeValidator

class FileUploadSerializer(serializers.Serializer):
    file = serializers.FileField(validators=[
        MaxFileSizeValidator(1024 * 1024),  # 1MB max
        MinFileSizeValidator(1024),         # 1KB min
    ])

Implementation

  • Added to rest_framework/validators.py
  • 77 new tests covering unit and integration scenarios
  • Documentation added to docs/api-guide/validators.md
  • All existing tests pass (1577 total)

Error Codes

  • max_file_size - Default for MaxFileSizeValidator
  • min_file_size - Default for MinFileSizeValidator

@mahdirahimi1999
feat: Add MaxFileSizeValidator and MinFileSizeValidator
6c9e226 
Add two new validators for enforcing file size constraints on uploaded files:

- MaxFileSizeValidator: Ensures files do not exceed a maximum size (in bytes)
- MinFileSizeValidator: Ensures files meet a minimum size (in bytes)

Both validators:
- Support custom error messages and codes
- Are deconstructible for migrations
- Include comprehensive unit and integration tests
- Work with FileField and ImageField
- Follow DRF conventions and patterns
@mahdirahimi1999
test: skip image file size validator tests if Pillow is not installed
888df27 
- Remove top-level PIL import from tests/test_validators.py
- Conditionally import PIL inside image-related tests and skip them if Pillow is unavailable
@mahdirahimi1999 mahdirahimi1999 mentioned this pull request Aug 6, 2025
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browniebroke
browniebroke reviewed Aug 8, 2025
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The validators which are included in DRF are quite limited at the moment, and I think it's because they have the same API as Django validators. Have you tried to contribute these to Django itself? Or publish as standalone package on PyPI? Feels like it could be useful to the wider Django community...

Personally, I can see some usefulness in a MaxFileSizeValidator, less so in the MinFileSizeValidator.

Going down one level to the code level, I can see that these are breaking away from our existing validators in some ways (@deconstructible, constructor accepting code as argument, ...).

@mahdirahimi1999
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mahdirahimi1999 commented Aug 8, 2025 •
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The validators which are included in DRF are quite limited at the moment, and I think it's because they have the same API as Django validators. Have you tried to contribute these to Django itself? Or publish as standalone package on PyPI? Feels like it could be useful to the wider Django community...

Personally, I can see some usefulness in a MaxFileSizeValidator, less so in the MinFileSizeValidator.

Going down one level to the code level, I can see that these are breaking away from our existing validators in some ways (@deconstructible, constructor accepting code as argument, ...).

Hi, thanks a lot for your thoughtful feedback!

Yes, I initially tried to contribute this directly to Django, but it was decided that such validators are better suited for third-party packages. You can see the related discussion here:

django/django#19636
https://code.djangoproject.com/ticket/34263
pypi profile

Thanks again for taking the time to review this!

@browniebroke
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As Carlton said a while back for Django, I don't see a compelling reason to include this in DRF core, these can very much live in a separate package that you can publish and install in your projects, and they would be useful to folks who use Django without DRF.

Thanks for the suggestion

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