WebP to PNG

This conversion almost always produces a larger file, and that is not a fault — it is the point. WebP is a compressed format built for the web; PNG is lossless and stores every pixel exactly. Going from one to the other means giving up the compression that made the WebP small.

A 200 KB WebP photograph commonly becomes a 1.5 MB PNG. If your goal was a smaller file, this is the wrong conversion; if your goal is compatibility with something that refuses WebP, it is exactly right.

The usual reason is software that has not caught up. Plenty of content management systems, older desktop applications, print workflows and internal tools still reject a WebP upload outright, even though every browser has displayed the format for years.

Converting to PNG is the safe answer because PNG is universally understood and lossless, so nothing degrades on the way. If file size matters more than universality, converting to JPEG instead will produce something far smaller — at the cost of transparency.

Lossless compression rewrites the file so it takes up less space while every pixel value survives exactly. Decode the result and you get the original back, byte for byte. PNG, GIF and lossless WebP work this way, and so does a ZIP archive.

Lossy compression throws information away on purpose. JPEG converts the image to a frequency representation, then discards the high-frequency detail your eye is least likely to miss. The result cannot be reversed: the discarded detail is gone. That is also why lossy formats reach file sizes lossless ones cannot approach — a photo saved as PNG is routinely five to ten times larger than the same photo saved as JPEG at a sensible quality.

Neither one is better. Photographs, with their smooth gradients and noise, suit lossy encoding. Screenshots, logos, line art, charts and anything with large flat areas and hard edges suit lossless encoding, because lossy encoders produce visible haloes around sharp boundaries.

JPEG has no alpha channel. It cannot store transparency in any form. When a transparent PNG is converted to JPEG the transparent pixels have to become something, and most tools silently fill them with black — which is why a logo exported to JPEG so often arrives with an unwanted dark box around it.

If your image has transparency you have three sensible options: keep it as PNG, use WebP (which supports alpha and is typically 25–35% smaller than PNG for the same image), or flatten it onto a known background colour deliberately rather than letting an encoder choose for you.

PNG's own compression is lossless and works best on images with few distinct colours and large uniform regions. A screenshot of a text document compresses beautifully. A photograph saved as PNG does not, because virtually every pixel differs from its neighbour and there is no redundancy for the algorithm to exploit.