Why WebP files cause trouble
WebP is an image format developed for the web, designed to make pages load faster by squeezing pictures into smaller files than JPG or PNG manage. Websites adopted it widely, which means a lot of the images you save from the internet now arrive as .webp whether you asked for that or not. Browsers handle them without complaint. Plenty of other software doesn’t: older photo editors, some word processors and presentation tools, print and photo-lab services, and upload forms that only list JPG and PNG as accepted types. The picture looks fine on screen and then refuses to open, attach or upload. Converting it to JPG solves that in one step.
What actually changes when you convert
A WebP can do several things a JPG can’t, so a few things change on the way over.
- Transparency is replaced by a colour. JPG has no transparent pixels, so the tool paints your chosen background colour underneath the image before saving. Anything that was see-through becomes that colour.
- Animation becomes stills. A JPG is a single picture, so an animated WebP becomes either its first frame or one JPG per frame, whichever you choose.
- The file is compressed again. WebP files are often already lossy, and JPG compresses lossily too, so the image goes through two rounds of compression. At high quality settings that is rarely visible, but it isn’t free.
- The size can go either way. WebP is usually the more compact format, so the JPG is often the larger of the two at similar visual quality. The size shown on each row is the real number for your file, not an estimate.
- Embedded details are dropped unless you keep them. Camera model, date and location are left out by default; the option to keep them appears when a file has any.
Choosing a quality setting
The slider runs from 30% to 100% and starts at 92%, a level where most photographs look the same as the source while the file stays reasonably small. Move it up if the picture is something you’ll print or edit further; move it down if it’s headed for a website or an email attachment and size matters more than the last bit of detail. Going all the way to 100% rarely looks any better than 92–95% and can make the file several times larger, so it’s seldom worth it. Pictures with sharp edges and small text (screenshots, diagrams, scanned pages) show compression damage sooner than photographs do, so they need a higher setting to stay clean. Because every row updates as you drag, the practical method is to lower the slider until the file is small enough, then check the thumbnail before you download.
Why this happens in your browser
The tool uses the decoder your browser already has to read the WebP, draws the result onto a canvas, and asks the browser to write that canvas out as a JPG. There’s no server step at any point, so nothing you convert is sent, stored or logged anywhere. It also means conversion is as quick as your own device, and you can convert a batch without waiting on an upload queue.
When JPG isn’t the right choice
JPG suits photographs. It’s a poor fit for logos, icons, screenshots and other flat-colour graphics with hard edges, where the compression leaves fuzzy halos and the file often isn’t even smaller. If you need transparency, or you’re converting something you’ll edit again and again, choose a lossless format such as PNG instead. And if you control the website the image is for, keeping it as WebP is usually the better call: the conversion here is for the times when something else in the chain simply doesn’t understand it.