WebP vs PNG: transparency, quality and file size

The format and the export mode are different choices

WebP supports both lossy and lossless encoding, as well as transparency. PNG is lossless and also supports transparency. JustToolset’s WebP export uses a quality setting for lossy encoding; it does not offer a separate lossless WebP mode.

Reference: MDN: image formats

A PNG can be larger without being better

WebP to PNG stores the decoded image as PNG. It preserves the decoded transparency, but cannot undo artifacts already present in a lossy WebP. The PNG may be larger because it uses a different encoding method. Compare actual bytes after processing instead of assuming a conversion will save space.

Choose a practical conversion

Use WebP to PNG when an editor or upload form requires PNG. Use PNG to WebP when the destination accepts WebP and you want to compare a smaller export. These converters handle supported still images; animated inputs are rejected rather than silently presented as complete animations.

1. Check which formats the destination accepts.
2. Convert the original image; adjust quality only for JPG or WebP output.
3. Inspect fine edges and transparency, then download the version that meets the destination’s requirements.