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 considers pixels with meaningful opacity when it builds each colour mask. Fully transparent pixels belong to no colour 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 renders the traced paths over the studio's dark surface, and transparent regions show the surface rather than a white box.

Semi-transparent edges (the soft anti-aliased fringe of a logo) are decided with a threshold: a pixel is either in a colour mask or not. A very soft glow or drop shadow therefore becomes a hard-edged band or disappears, depending on its opacity. That is a limitation of tracing flat regions, not something a setting can restore.

Why white details survive background removal

"Remove background" is a flood fill from the picture's edges. It looks at the border, finds the dominant border colour, and marks every connected pixel of that colour starting from the edges as transparent. 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 a deliberate design choice and is covered by a regression test: a white logo detail enclosed by darker artwork must still be present after removal. If you have seen other tools erase every white pixel, that is a different technique (colour 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 — the flood reaches it 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 colours. A white icon exported on a white canvas is, to the quantiser, 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 grey or a colour 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.
  • Rasterise 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 behaviour worth knowing

  • The sketch preset converts the picture to black and white by luminance before tracing; alpha is still respected, so transparent areas stay transparent, but white artwork becomes "background" in that mode.
  • The preview PNG is watermarked and rasterised; only the unlocked SVG carries the vector paths and the true transparency.