Transparent input, transparent output

PNG and WebP can store an alpha channel — per-pixel opacity. JPEG cannot. When you upload a PNG or WebP, the tracer decodes the alpha and only gives a color to pixels that are more than half opaque. Pixels below that belong to no color and produce no path, so the empty area around a cut-out logo stays empty in the SVG. The output <svg> has no background rectangle; whatever you place it on shows through.

You can verify this in the preview: the result panel draws the traced paths over a checkerboard, and transparent regions show the checkerboard rather than a white box.

Semi-transparent pixels are handled in two steps. First, every pixel is either in a color or not, at the half-opaque mark: the soft anti-aliased rim of a logo is cut there, so the outline lands where the edge is half covered. Second, each color keeps the opacity of its ink, measured inside its shapes rather than at the soft rim. Solid ink is written fully opaque, so black text on a transparent logo stays black and not a lighter gray. A color that is see-through in the source — a soft drop shadow or a tinted overlay — is written with that opacity as its fill-opacity, so a shadow traces as one flat, evenly semi-transparent shape (for example at 54 % opacity). What a trace cannot keep is the fade itself: the shadow's faint outer part, below half opacity, is left out, and the shape it becomes has a crisp edge and one even opacity instead of a gradual fade.

An otter logo with a soft drop shadow on a checkerboard; its traced SVG on the checkerboard; and the same SVG on a light green background, where the shadow shows as one see-through shape

A transparent PNG of our otter logo with a soft drop shadow added (left), the SVG traced from it over a checkerboard (middle) and over a color (right). There is no background box, the white of the eyes is kept, and the shadow became flat shapes at 60 % opacity, with crisp edges where the PNG had a fade.

Why white details survive background removal

"Remove background" works inward from the picture's edges. It looks at a band along the image border, takes the one or two colors that each cover at least 15 % of it, and starting from the edges marks every connected pixel of those colors — and of colors close to them — as transparent. It then also clears the soft fringe where that backdrop meets the artwork (pixels right next to the removed area that are still close to the backdrop color) and small specks that touch the image edge. Anything not connected to the border is untouched — the white counter of an "A", the white highlight in a badge, the white gap between two stripes.

This is deliberate: a white logo detail enclosed by darker artwork is still there after removal. If you have seen other tools erase every white pixel, that is a different technique (color keying), and it is why "remove background" elsewhere can hollow out a design.

The flip side: if the enclosed white region is connected to the border — because the outline has a gap of even one pixel — removal gets in through the gap and removes it. Repair the gap in the source, or leave removal off and delete the background path in the editor afterwards.

White artwork on a white background

The tracer cannot separate identical colors. A white icon exported on a white canvas is, to the tracer, one white region, and the result is either a single white rectangle or an empty conversion ("No vector paths could be produced"). Fix it before uploading:

  1. In any image editor, put the icon on a solid, strongly contrasting backdrop (dark gray or a color that does not appear in the icon).
  2. Upload with Remove background on. The backdrop is connected to the edges, so it goes; the white icon stays.
  3. If the icon has enclosed transparent areas that must stay transparent, export it as a PNG with real alpha instead, so no backdrop is needed at all.

Checking alpha in the result

  • Open the downloaded SVG in a browser: the page background (white by default) shows through transparent areas.
  • Rasterize it with the SVG to PNG tool — the output is RGBA and keeps the transparency.
  • Open the file in a text editor: there is no full-size background path unless your source had an opaque background and removal was off.

Related behavior worth knowing

  • The Line art / Stencil preset judges every pixel by its brightness as it would look on white paper: dark becomes black ink, light becomes white paper, and transparent areas stay transparent. White artwork therefore comes out as white paper, not as ink, and the semi-transparent edge of a dark line on a transparent background is left out rather than turned into a pale halo.
  • The preview PNG is watermarked and rasterized; only the unlocked SVG carries the vector paths and the true transparency.