The Technical Internals of Client-Side PDF Manifestation

At FilesCenter, our core philosophy is Privacy by Design. To achieve this, we had to solve a massive engineering challenge: How do you perform heavy-duty document processing (like merging 500MB PDFs or OCR) entirely within the browser's sandbox?

The answer lies in the intersection of WebAssembly (Wasm) and modern browser storage APIs.

The Architecture of In-Browser Processing

Unlike traditional SaaS tools that upload your files to a cloud server, FilesCenter brings the server to you. We've ported industrial-grade C++ and Rust libraries to WebAssembly.

1. WebAssembly: The Heavy Lifter

When you select a file, we initialize a Wasm instance. This instance has its own isolated memory space. By using SharedArrayBuffer, we can pass large binary blobs (literal fragments of your PDF) directly to the Wasm module without the overhead of copying data across the bridge.

javascript
// A conceptual look at our memory management
const memory = new WebAssembly.Memory({
  initial: 256,
  maximum: 2048,
  shared: true
});

const importObject = { 
  env: { memory: memory } 
};

WebAssembly.instantiate(module, importObject).then(instance => {
  // Processing happens here at near-native speeds
  instance.exports.merge_pdfs(ptr, size);
});

2. The PDF Object Tree

PDFs aren't just images; they are complex hierarchical structures. Our engine parses these into a DOM-like tree. This allows us to perform operations like Rearranging Pages or Deleting Sensitive Metadata in milliseconds.

Why This Matters for Your Privacy

Because your files never leave your computer:

• Zero Latency: No waiting for uploads.
• Max Security: Even we can't see what's in your documents.
• Offline Capability: FilesCenter works in an airplane or a bunker.

Looking Forward: Client-Side OCR

We are currently working on a Tesseract-based Wasm module that will allow you to perform OCR on your scanned documents without sending a single byte to the cloud. Stay tuned to our Engineering Blog for the technical breakdown when it launches.