WebP has quietly become one of the most common image formats on the web without most people noticing, because it’s rarely something you choose — it’s something a website chooses for you, serving WebP by default to anyone whose browser supports it (which by now is nearly everyone) in order to load faster. The friction shows up later, once you’ve saved or downloaded that image and try to use it somewhere that isn’t a modern web browser.
Why WebP is everywhere but not universally supported
Google introduced WebP specifically to beat JPG and PNG at their own jobs — smaller files at comparable quality, with support for both lossy compression (for photos) and lossless compression with transparency (for graphics) in a single format, something JPG and PNG together used to require two separate formats for. Browser support is now nearly universal, which is why so many sites switched to serving it as their default image format for faster page loads. The gap is everything outside the browser: a meaningful amount of desktop software, especially anything older or more specialized, was built before WebP existed or before its support became standard, and either can’t open it at all or handles it inconsistently.
This creates a specific, recurring situation: you find an image on a website, right-click and save it, and end up with a .webp file that won’t open in whatever you actually wanted to use it for — an older photo editor, certain design tools, some office software, or a printing service’s upload page.
Why PNG specifically, rather than JPG
If you’re converting away from WebP for compatibility, you have a choice of target format, and it matters which you pick. PNG is the better choice whenever the original WebP image has transparency you need to keep — a logo, an icon, a graphic meant to sit on top of other content. JPG has no way to represent transparent pixels at all, so converting a transparent WebP to JPG would silently flatten any transparent areas onto a solid (usually white) background, which is rarely what you actually want.
If the image doesn’t have transparency and is a genuine photograph rather than a graphic, JPG is usually the more practical target instead — smaller resulting file, and just as widely supported as PNG. PNG’s main advantage, losslessness, matters most for flat-color graphics with sharp edges and text, exactly the content WebP’s lossless mode is also good at — so converting a lossless WebP graphic to PNG tends to be a clean, low-loss conversion.
What actually happens during conversion, and why size sometimes goes up
Converting from WebP to PNG means decoding WebP’s compressed image data back into raw pixels, then re-encoding those pixels using PNG’s lossless compression method. Because WebP’s own compression (in either of its modes) is generally more space-efficient than PNG’s, it’s completely normal for the PNG output to end up noticeably larger than the original WebP file, even though no extra detail was added — PNG is just a less compact way of storing the same information. This is a reasonable cost to pay for compatibility, not a sign that anything went wrong in the conversion.