Why In-Browser Image Editing Is Actually Private (and How Filezy Does It)

Every time you drag a photo onto a “free online image compressor”, you're copying that file over the public internet to someone else's computer. Most sites are transparent about it — the progress bar literally says Uploading…. What's less obvious is that many of them keep the file for hours, days, or forever, depending on their retention policy.

Filezy does notwork that way, and the architecture is worth explaining because it's the same thing that makes the editor feel fast.

Two kinds of tools, one rule

Every tool in Filezy is tagged with a runtime badge so you can see at a glance where the work happens:

• Local tools run entirely inside your browser. Your image never leaves your device. This covers strip metadata, logo watermark, face blur, background removal (using @imgly/background-removalwith an ONNX model), and the 2×/4× upscaler (ESRGAN via UpscalerJS/TensorFlow.js).
• Server tools send your image to a stateless Sharp pipeline that processes the pixels in memory and returns the result. Nothing is written to disk, nothing is logged, nothing is retained past the request. This covers compress, crop, rotate, brightness/contrast/saturation, sharpen, text watermark, add-border, and round-corners.

The rule: if it can run well in the browser, it does. The only operation that uses a server today is JPEG compression via MozJPEG — a quality improvement that isn't available in the browser. Everything else (crop, rotate, adjust, sharpen, watermark, borders, rounded corners, background removal, upscale) runs entirely client-side.

Why “in your browser” is not hand-waving

A lot of sites say “runs in your browser” and then quietly upload anyway. You can verify Filezy yourself in 30 seconds:

1. Open your browser's DevTools, switch to the Network tab.
2. Open /strip-metadata, /remove-background, or the logo watermark panel in the Workshop.
3. Drop an image and run the tool. Watch Network.

You'll see the model weights download once (for the AI tools), and after that, no image data crosses the wire. The edit happens via Canvas or WebAssembly on your own CPU/GPU.

What makes this fast

Keeping work local sounds like it should be slow — surely our server is faster than your laptop? Two reasons it's usually not:

1. No round-trip. The slowest part of any online tool is uploading the file. A 5 MB photo over a typical home connection is 2-8 seconds before the work even starts. Skipping that means the editor feels instant on small images.
2. Your device has a GPU now.Modern browsers (Chrome, Edge, Firefox, Safari) ship with WebGL, WebGPU, and WASM SIMD. The AI background remover runs on your GPU via ONNX WebGL backend; a mid-range laptop hits 200–400ms on a 4K photo.

What actually leaves your device?

A one-line summary per tool:

Try it

If you're here because you're tired of uploading photos to get them cropped, compressed, or cleaned up, drop an image into the Filezy Workshop. Stack crop, rotate, watermark, and remove background in one pass — and keep the original on your device the whole time.