What actually happened
When you save an image from a web page, your browser writes whatever the site sent it. It does not convert on the way out. If the page was serving a WebP — and a great many now are — a WebP is what lands in your downloads folder, whatever the picture looked like on screen.
This catches people out because the image looked completely normal in the browser. It was normal. Browsers have read WebP for years. The problem only appears at the next step, when the file meets something that is not a browser.
Why sites serve WebP at all
Because it is smaller. At the same visible quality a WebP is typically 25–35% lighter than the equivalent JPG, and considerably lighter again than a PNG of the same photograph. On a page carrying a dozen images that is a real difference to how quickly the page appears, which is why it has become a default rather than an experiment.
From the site's side nothing is wrong. It served a modern format to a browser that understands it. The format was never chosen with your photo library in mind.
Who refuses it, and why
The refusals cluster in three places, and they are all the same story: the software predates the format, or has no reason to have added it.
- Older photo viewers and editors. Anything that has not been updated in a few years may simply not know the format exists.
- Upload forms. A form that accepts
.jpgand.pngonly will reject a WebP at the door, and the error message rarely explains why. - Print shops and document workflows. Print pipelines are conservative on purpose; they standardise on formats that have behaved predictably for decades.
None of this means the file is damaged. A WebP that a print shop rejects is a perfectly intact image — it is just wearing a jacket the doorman does not recognise.
What to do about it
There are two honest options, and which is right depends on whether this is a one-off or a habit.
Convert the file. This is the answer nearly everyone wants. Converting to JPG gets you a file that opens anywhere; converting to PNG is the right choice if the image has a transparent background, because JPG cannot store transparency and will fill it with white.
Worth knowing: because your browser already decodes WebP, a converter does not need to send the file anywhere. The one on this site does the work on your own machine — there is no upload step to wait for and no server holding your image afterwards. You can watch the network tab stay silent while it runs.
Ask the site for a different format. Sometimes possible, usually not. A few sites offer a download button with a format choice, and screenshotting the image gives you a PNG at the cost of quality and the original dimensions. Neither is reliable enough to plan around.
When to keep the WebP
If the image is going onto a website of your own, keep it. WebP is doing exactly its job there, and converting it to JPG would make the file larger for no gain. The same applies if you are only ever going to look at it in a browser.
Convert when the file has to leave the browser: to a person, a printer, a form, or an older program. That is the whole rule.