Make a logo file smaller and resize it, keeping the transparent background.
Yes - PNG and WebP both keep transparency, and this tool only offers those two formats. The result panel tells you whether a transparent background was found and preserved. JPEG is not offered because it fills transparent areas with white.
WebP is usually much smaller at the same quality and also keeps transparency - best for websites. PNG is lossless and the safest choice for print or editing later, but a PNG can come out larger than your original if the original was already well compressed.
No - if your logo is already small or well compressed, the output can be the same size or larger, and the tool will say so honestly instead of pretending it shrank. In that case try WebP or a smaller size preset.
No - everything runs in your browser and the image never leaves your device.