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Why WebP to PNG Makes Files Bigger

Convert a WebP image to PNG and the result is often noticeably larger than the source, sometimes several times larger. That's expected behavior, not a broken conversion.

Two different compression approaches

WebP's lossless mode and lossy mode both use more modern, more efficient compression techniques than PNG. WebP was designed specifically to beat PNG and JPEG at their own jobs. PNG uses an older lossless compression scheme (DEFLATE, the same family used by ZIP files) that simply doesn't squeeze image data as tightly as WebP's algorithm does, even when both are storing the image losslessly with zero quality loss.

If the source was lossy WebP

If the original WebP was saved in lossy mode (common for photos), converting to PNG doesn't just re-pack the same data more loosely. It takes the already-decoded pixels and stores all of them losslessly, including any compression artifacts from the original lossy encode. You're not recovering detail the lossy WebP threw away; you're just storing what's left, uncompressed-relative-to-WebP, which naturally takes more space.

So why convert at all?

Not every tool or platform accepts WebP. Older image editors, some CMS upload systems, and certain print workflows still expect PNG or JPEG specifically. The size increase is the cost of that compatibility, the same tradeoff as HEIC-to-JPG conversion for photos.

If file size matters more than compatibility

If you don't specifically need PNG, keeping the file as WebP (or converting a photo to JPEG instead, which also compresses more efficiently than PNG for photographic content) will generally produce a smaller result than PNG for the same image.

Convert WebP to PNG and read the full WebP vs PNG vs JPG comparison for when each format actually wins.