The saving depends on the picture
PNG compresses by finding repetition, which works brilliantly for flat colour and badly for photographs. That is why the same conversion produces wildly different results:
| PNG contents | Typical saving | | --- | --- | | Photograph | 60–80% | | Screenshot with text | 30–50% | | Flat logo or icon | 10–25% | | Already-tiny sprite | close to nothing |
If your saving is disappointing, that usually means the PNG was well-suited to PNG — which is a good outcome, not a failure.
Transparency survives
This is the reason to convert to WebP rather than JPG. JPG has no alpha channel at all, so a transparent PNG converted to JPG gets a solid background painted behind it. WebP keeps the transparency exactly.
Lossless or lossy
WebP can do both, and this page lets you choose. At quality 100 the result is lossless — the pixels are identical to the PNG and only the encoding changed. Below that, WebP starts discarding detail, which is usually the right trade for a photograph and the wrong one for an icon with hard edges.
Questions
Is transparency preserved?+
Yes. WebP has a full alpha channel, so a transparent PNG converts without a background being painted in. This is the main reason to choose WebP over JPG for logos and UI assets.
How much smaller is it?+
It depends entirely on what the PNG contains. A photograph saved as PNG often drops by 60–80%, because PNG is the wrong format for photographs in the first place. A flat-colour logo may only drop by 10–20%, because PNG is already good at those.
Is anything lost?+
Only if you choose a quality below 100. WebP can be lossless, in which case the pixels are identical and the file is simply smaller. The quality slider on this page controls that — at 100 the conversion is exact.