The problem with most "blur a photo" tools
Search for "blur face in photo online" and most of the results work the same way: you drop your image into a box on the page, and it gets sent to a server somewhere to be processed. For a screenshot with someone's face, address, or license plate in it - exactly the kind of image you're trying to redact for privacy - that's a strange thing to do. You're uploading the sensitive part to a third party specifically to hide it from everyone else.
For something as simple as blurring a region of an image, there's no reason the file needs to leave your device at all. A <canvas> element in the browser can read pixel data, apply a blur filter, and let you download the result - the entire operation happens locally.
Doing it in your browser
That's what Blur Brush does: drag over the area you want to obscure, and it blurs that region directly on the canvas. Nothing is uploaded, because there's no server call to make in the first place - open your browser's network tab while using it and you won't see the image go anywhere.
A few practical tips for a clean result:
- Blur the whole feature, not just its center. A half-blurred face is often still recognizable. Drag a little past the edges of what you're hiding.
- Faces and license plates need more blur than you'd think. A light blur can still be reversible-looking to the eye even if it technically obscures detail. When in doubt, go heavier.
- Check the result at full size before sharing. A blur that looks sufficient in a small preview can look thinner once someone zooms in on the actual image.
Why this matters beyond just this one tool
This isn't really about one blur tool - it's about noticing how much of the "free tool" ecosystem online defaults to "upload your file to our server" for tasks that don't need it. Rotating an image, merging PDFs, formatting JSON, blurring a region - these are all things a browser can do on its own. If a tool doesn't need your file to leave your device, it shouldn't ask for it to.