File Upload Handling

This handles the full lifecycle of file uploads: validation, sanitization, virus scanning, storage, and serving. You get reference implementations for Flask, FastAPI, and Express with Multer, plus S3 integration patterns. The examples cover the security essentials like MIME type validation, secure filename generation, and directory traversal prevention. Most useful when you're building upload features from scratch and want to avoid the common security pitfalls. The emphasis on signed URLs and CDN integration shows it's thinking beyond just accepting files. Solid starting point if you need more than a basic multipart form handler.

skills.sh installs: 483
GitHub stars: 379
last updated: Aug 21, 2026

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Install

$ npx -y skills add aj-geddes/useful-ai-prompts --skill file-upload-handling --agent claude-code

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Overview

Build secure and robust file upload systems with validation, sanitization, virus scanning, efficient storage management, CDN integration, and proper file serving mechanisms across different backend frameworks.

When to Use

Implementing file upload features
Managing user-uploaded documents
Storing and serving media files
Implementing profile picture uploads
Building document management systems
Handling bulk file imports

Quick Start

Minimal working example:

# config.py
import os

class Config:
    MAX_CONTENT_LENGTH = 50 * 1024 * 1024  # 50 MB
    UPLOAD_FOLDER = 'uploads'
    ALLOWED_EXTENSIONS = {'txt', 'pdf', 'png', 'jpg', 'jpeg', 'gif', 'docx', 'doc'}
    UPLOAD_DIRECTORY = os.path.join(os.path.dirname(__file__), UPLOAD_FOLDER)

# file_service.py
import os
import mimetypes
import hashlib
import secrets
from werkzeug.utils import secure_filename
from datetime import datetime
import magic
import aiofiles

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