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How It Works

Every brevtool runs entirely inside your browser. Here is the full technical explanation of how — and why — that matters for your privacy.

Your Files Never Leave Your Device

When you use a tool like Merge PDF or Compress Image on brevtool, your file is read directly from your local storage into your browser's memory. It is processed there, and the output is written back into browser memory. The resulting file is then offered to you as a download — directly from your own browser.

At no point during this process does any data travel over the network. There is no upload request, no POST to a server endpoint, no temporary storage in the cloud. If you open your browser's developer tools and inspect the Network tab while using a brevtool, you will see zero file-related network requests.

This is a verifiable, architectural guarantee — not a policy claim. The code that processes your files lives and runs in the same browser tab you are using. It has no mechanism to send your files anywhere because it never needs to.

Powered by WebAssembly

WebAssembly (WASM) is a binary instruction format that modern browsers can execute at near-native speed. Originally designed for high-performance applications like games and multimedia software, WASM has made it possible to run complex, production-grade processing libraries entirely in the browser.

brevtool uses several battle-tested libraries compiled to WebAssembly:

  • pdf-lib

    A pure-JavaScript PDF creation and modification library. Used for merging, splitting, and manipulating PDF documents. Runs entirely in the browser with no native dependencies.

  • Canvas API

    The browser's built-in 2D rendering engine. Used for all image operations — compression, resizing, and format conversion (PNG, JPG, WebP). No external library required; this is part of every modern browser.

  • ffmpeg.wasm

    FFmpeg — the industry-standard multimedia processing tool — compiled to WebAssembly. Powers MP4 to MP3 conversion and Video to GIF conversion. The same codec quality you would get from a desktop application, running in your browser tab.

These libraries are loaded once and cached by your browser. Subsequent uses of the same tool are near-instant since the WASM binary is already in memory.

What Happens When You Use a Tool

Here is the exact sequence of events when you use a file tool like Compress PDF:

  1. 1
    File selected

    You choose a file via the file picker or drag-and-drop. The browser creates a File object in memory — this file has not moved anywhere. It exists only in your browser's memory.

  2. 2
    Read into browser memory

    The FileReader API reads the raw bytes of the file into an ArrayBuffer — a typed byte array held in your browser's RAM. Still no network activity.

  3. 3
    Processed via WASM or Canvas

    The ArrayBuffer is passed to the processing library (pdf-lib, Canvas API, or ffmpeg.wasm). The library performs the operation — compression, merging, format conversion — and returns a new ArrayBuffer containing the result.

  4. 4
    Result generated in memory

    The output ArrayBuffer is wrapped in a Blob object and a temporary object URL is created pointing to it. The original file is still untouched in its original location on your device.

  5. 5
    Download from browser

    The browser triggers a download from the object URL. The file transfers from browser memory to your download folder — entirely on your device. The object URL is then revoked and the memory is freed.

No Server, No Upload, No Risk

Most online tool sites operate a backend server that receives your files, processes them, stores a temporary copy, and sends the result back. This means your file traverses the internet at least twice — once on upload, once on download — and sits on a third-party server for some period of time.

brevtool has no such server. There is no infrastructure that receives files. There is no S3 bucket, no temporary storage, no processing queue. The brevtool servers only serve the application code — the HTML, JavaScript, and WASM binaries — to your browser. After that, your browser does all the work.

This means:

  • A data breach of brevtool's servers cannot expose your files — we never had them.
  • Processing is as fast as your device, not limited by server capacity or queue position.
  • You can use brevtool offline (after the page has loaded) for most tools.
  • There is no "your file will be deleted in 24 hours" because there is no file on our end to delete.

Client-side processing is not a marketing claim. It is the only architecture that can make these guarantees honestly. We built brevtool this way because it was the right way to build it.