Compress a PNG While Keeping Its Transparent Background

Keep the format when you need transparency

JPG does not store a transparent background. Converting a transparent PNG to JPG adds a background color. If the destination needs transparency, keep the output as PNG and inspect the result against both light and dark backgrounds.

Start with pixel-preserving re-encoding

The default PNG mode re-encodes supported decoded pixels. That is different from preserving the original file byte for byte. Metadata and embedded profile behavior may change. The first release accepts static 8-bit PNG files within its displayed input and pixel limits; it rejects unsupported variants.

Reduce colors only when the visual tradeoff is acceptable

The reduced-color mode is lossy. It can keep transparent areas while changing color detail in gradients, fine edges or anti-aliased text. Compare the actual preview with the source. Keeping transparency is not the same promise as keeping every color.

Resize when the dimensions are much larger than needed

Resizing reduces pixel dimensions; compression changes the stored representation. If an upload only needs a small logo, start with a suitably sized image rather than forcing a large source into an extreme file-size target. Keep a full-size original for future uses.

Check the actual bytes and keep the original when useful

An already optimized PNG may not become smaller. The compressor compares the new result with the source and keeps the original download when re-encoding does not reduce its size. The PNG mode does not use the JPG/WebP target-KB control. A useful output is one that satisfies the destination’s requirements and still looks acceptable.

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