How Do I Add File Uploads to My App?
You built an app with Claude, ChatGPT, Bolt, or Lovable and you need users to be able to upload files. Maybe profile photos. Maybe documents. Maybe CSV files…
You built an app with Claude, ChatGPT, Bolt, or Lovable and you need users to be able to upload files. Maybe profile photos. Maybe documents. Maybe CSV files for data import. File uploads seem like they should be straightforward but they involve several moving parts that catch most first-time builders off guard. Here is exactly how file uploads work, where uploaded files should go, and how to implement it without a developer.
The Two Parts of File Uploading
Adding file uploads involves solving two separate problems:
Part 1: Accepting the file. Your app needs a way to receive the file from the user’s browser, process it, and handle it without crashing.
Part 2: Storing the file. Files cannot just live in your app’s code. They need a permanent home, usually a cloud storage service, where they can be retrieved later.
Most tutorials focus on Part 1 and gloss over Part 2, which is why so many first implementations seem to work and then break when the app is deployed or restarted.
Where Uploaded Files Should Live
Do not store uploaded files directly in your app’s directory.
When you deploy to Vercel, Netlify, or most hosting platforms, your app’s file system is temporary. Every time you redeploy, the file system resets. Any files saved directly to your app’s directory disappear.
The right answer is cloud storage: a service designed specifically to store files permanently and serve them reliably.
The three most common options:
Supabase Storage is the easiest option if you are already using Supabase as your database. It is built in, free for up to 1GB, and your AI can write the integration code quickly. Start here.
AWS S3 is the most established cloud storage service. More complex to set up than Supabase but handles any volume. If your AI suggests S3, ask it to walk you through the setup step by step.
Cloudflare R2 is a newer S3-compatible storage service with no egress fees, meaning you do not pay when files are downloaded. Often cheaper than S3 for apps with lots of file downloads.
How to Implement File Uploads
Tell your AI exactly what you need:
“I want to add file upload functionality to my app. Users should be able to upload [describe the file type, e.g. images up to 5MB / PDF documents]. Store the uploaded files in [Supabase Storage / AWS S3] and save the file URL to my database so I can retrieve them later. Can you write the frontend upload component and the backend code to handle the upload and storage?”
Your AI will write:
- A file input element for your frontend
- Backend code to receive the file
- Code to upload it to your chosen storage service
- Database logic to save the file URL
Important Things to Handle
File size limits. Set a maximum file size to prevent huge files from crashing your app or exhausting your storage. Ask your AI to add validation that rejects files over your chosen limit.
File type validation. Only accept the file types you actually need. If you only want images, reject PDFs. If you only want CSVs, reject images. Ask your AI to add file type checking on both the frontend and backend.
Security. Never execute uploaded files or trust their contents blindly. Ask your AI: “Are there any security considerations I should handle for file uploads in my app?”
Loading state. File uploads take time. Your UI should show the user that the upload is in progress and confirm when it is complete. Ask your AI to add a loading indicator and success state to your upload component.
The One Thing to Remember
File uploads have two parts: accepting the file and storing it permanently. Store files in cloud storage, not in your app’s directory. Supabase Storage is the simplest starting point. Give your AI a complete description of what you need, including file types and size limits, and it will write the entire implementation. Always add file size and type validation to prevent abuse.
Want your file-handling app running reliably in production? → Snapdock
New here? These might help: Why does my app lose all its data when I restart it? → What is a .env file? Why your app needs one and how to use it. →