How to Create a File Upload System
Build a secure file upload system with direct-to-cloud uploads, image processing, and CDN delivery.
What You'll Learn
This intermediate-level guide walks you through how to create a file upload system step by step. Estimated time: 10 min.
Step 1: Choose your storage backend
Select AWS S3, Cloudflare R2, or Google Cloud Storage based on pricing, performance, and feature requirements.
Step 2: Implement presigned uploads
Generate presigned URLs on your server so clients upload directly to cloud storage, bypassing your server for large files.
Step 3: Add file validation
Validate file types, sizes, and content on both client and server side to prevent malicious uploads.
Step 4: Implement image processing
Add automatic image resizing, format conversion to WebP, and thumbnail generation using Sharp or cloud-based services.
Step 5: Set up CDN delivery
Configure CloudFront or Cloudflare CDN in front of your storage for fast global file delivery with caching.
Frequently Asked Questions
Should I upload through my server or directly to cloud?▾
Direct-to-cloud with presigned URLs for files over 1MB. Through your server for small files that need immediate processing. Direct upload reduces server load significantly.
How do I handle large file uploads?▾
Use multipart uploads for files over 100MB, implement resumable uploads for unreliable connections, and show progress bars for better user experience.
How do I secure uploaded files?▾
Validate file types server-side by checking magic bytes, scan for malware, use unique filenames to prevent enumeration, and set proper access controls on your storage bucket.