Why I Built a 100% Private File Converter Using WebAssembly (No Server Uploads)
Source: Dev.to
The Problem with Cloud Processing
Most “free” online file converters are a privacy nightmare. When you upload a PDF or an image to a service like ConvertMyFile.com, your sensitive data sits on a random server.
Traditional tools use the Upload‑Process‑Download model. This is slow (due to upload speeds) and risky for privacy. If you are merging a legal contract or a personal photo, you shouldn’t have to trust a third‑party server.
The Solution: Client‑Side WebAssembly
To make FileMint truly private, zero files ever leave the user’s browser. This is achieved with:
- WebAssembly (WASM) – heavy lifting (PDF merging, image compression) using C++ and Rust libraries compiled to WASM, giving near‑native speeds.
- JavaScript File API – handles file streams locally without a backend.
- React & Tailwind – a clean, fast UI that works on mobile and desktop.
Why Privacy‑First Matters
Since processing happens in the user’s RAM:
- Zero latency – no waiting for files to upload.
- Zero data leaks – the developer cannot see your files, even if they wanted to.
- Offline access – once the site is loaded, it works without an internet connection.
What’s Next?
I’m currently exploring adding OCR (Optical Character Recognition) entirely in the browser using Tesseract.js.
Check out the project here:
I’d love to hear your thoughts on the architecture. How are you handling file privacy in your web apps?