Is my image uploaded?

No. It is drawn to a canvas in your browser and packed into a ZIP locally. Nothing leaves the page.

Is favicon.ico a real ICO file?

Yes. It is a proper multi-image ICO containing 16, 32 and 48 pixel versions, not a renamed PNG.

Square and at least 512x512. Smaller works but 16x16 loses fine detail.

Browser tab favicons are fine transparent. For the Apple and Android icons choose a background colour, or iOS shows the transparent areas as black.

The ZIP contents go in your site root folder, then paste the HTML snippet into your page head.

Once the page has loaded, yes. All the resizing and packing runs on your device.

Background ?

Padding ? 0%

Corners ? Square

Drop an image, or

PNG, JPG, WebP or SVG. A square image at least 512×512 gives the sharpest result.

It is processed on your device. Nothing is uploaded.