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How It Works

Favtoo is fundamentally different from traditional online file tools. Instead of uploading your files to a server for processing, everything happens right inside your web browser. Here's how.

1

You Select a File

When you click "Choose File" or drag and drop, your browser reads the file using the File API. The file's contents stay in your browser's memory — they are never transmitted to a Favtoo server, never copied to any third-party service, and never logged.

2

Browser Processes Locally

The tool processes your file using JavaScript and WebAssembly engines running entirely in your browser. A Web Worker handles the heavy lifting so the UI stays responsive.

3

You Download the Result

The processed file is created in memory and offered as a download. Once you save it, the browser releases the memory. No data persists on any server.

Technologies We Use

WebAssembly (WASM)

Compiled C/C++ libraries (like pdf-lib, libheif) run at near-native speed in your browser. This is what makes heavy operations like PDF compression and image conversion fast.

Canvas API

Used for image resizing, cropping, format conversion, and visual manipulation. The browser's native rendering engine handles pixel operations efficiently.

Web Workers

Heavy processing runs on a background thread so the page remains responsive. You can continue browsing or even start another tool while processing.

File & Blob API

Files are read and written using standard browser APIs. Object URLs create downloadable links without any server round-trip.

What This Means for Privacy

  • Your file contents are never transmitted over the network. The Favtoo page itself, like any website, is loaded over the network and a privacy-friendly Plausible page-view ping is recorded — but the file you process is not part of either of those.
  • We cannot see, access, or store your files
  • Processing works offline once the page is loaded
  • Closing the tab releases all file data from memory
  • No account or login is ever required

Limitations

Browser-based processing is powerful but has some limitations compared to server-side tools:

  • File size limits: Processing large files depends on your device's available RAM rather than any server quota. The file picker on each tool sets a category-wide ceiling that is well above what mainstream free-tier competitors allow (1 GB for PDFs and audio, 512 MB for images, 4 GB for video). See the file size limits page for the full breakdown.
  • Device performance: Older devices may process files more slowly.
  • Browser support: Modern browsers (Chrome 90+, Firefox 90+, Safari 15+, Edge 90+) are required. See our Supported Browsers page.