File Upload Handling: Secure and Scalable Uploads

File uploads require careful handling for security and scalability. This guide covers patterns for safe, efficient file processing.

Basic Upload with Multer#

Upload to S3#

Presigned URLs for Direct Upload#

File Validation#

Image Processing#

Chunked Uploads#

Frontend Upload with Progress#

Security Checklist#

• ✅ Validate file type by magic bytes, not extension
• ✅ Limit file size
• ✅ Generate random filenames
• ✅ Store files outside web root
• ✅ Scan for viruses
• ✅ Validate image dimensions
• ✅ Set proper content-type headers
• ✅ Use presigned URLs for direct upload

Conclusion#

File uploads require validation, secure storage, and efficient processing. Use presigned URLs for large files, validate thoroughly before processing, and store files in object storage like S3 for scalability.