Why the file you saved is a WebP
WebP is an image format built for the web. A photograph in WebP is often noticeably smaller than the same photograph in JPEG, so blogs, shops, and news sites send it when the browser says it can cope. You do not choose that. You open an article, the picture looks normal, you right-click and save, and the download is a .webp. Google image results do this constantly. So do a lot of CDNs that rewrite every upload into a modern format on the way out.
The annoyance is downstream. A print shop's upload form lists JPEG and PNG. PowerPoint on an older install shrugs. A desktop publisher from a few years ago has never heard of the extension. Slack or a mail client shows a generic icon to the person you sent it to. The picture was fine in Chrome. The file is the problem. JPEG is the format those other tools already agreed on, which is the only reason to convert.
What you give up, and what you do not
You do not get a better photograph. Lossy WebP has already thrown away detail, especially around text, foliage, and high-contrast edges. Encoding a JPEG freezes those pixels in a more compatible file. It does not sharpen them, and it does not undo the site's compression. If the WebP was saved at a high quality, a JPEG at 92 will look very close and may even be larger. If the WebP was a tiny thumbnail blown up by the page layout, the JPEG will be a larger file of the same soft picture.
The quality slider controls that second compression. It starts at 92. Move it down when the JPEG only has to survive a chat message. Leave it up when someone will crop or print it. Moving the slider after a conversion encodes again from the bitmap already in memory. The original WebP is not sent anywhere to be recompressed on a server.
Transparency does not survive. JPEG has no alpha channel, so this page paints a white background and then draws the image. A product photo shot on white looks the same. A logo, a sticker, or a screenshot with rounded corners and a transparent surround will grow a white box. That is the correct JPEG behavior, and it is the wrong format for those files. Use WebP to PNG when the empty areas have to stay empty. The preview's checkerboard lets you see transparency before you commit to JPEG.
Metadata, animation, and batches
The JPEG is newly drawn, so EXIF and XMP from the WebP are not copied. That includes GPS coordinates and capture time if a camera or an editor had written them. Color appearance follows what the browser decoded. Animated WebP becomes one frame, the bitmap the browser returns, not a video and not a zip of every frame. For the usual case — a still photo or a diagram saved from a web page — one frame is the whole file.
You can drop in a folder's worth of downloads. Each row reports its own size and status. A file that is not a WebP, or a WebP this browser cannot decode, fails on its own line and does not stop the others. Download all as ZIP packs the JPEGs that worked. There is no watermark and no account limit. A very large set is limited by the tab's memory.
FromHEIC does not keep the images. There is no upload step hiding behind the button. If a workflow needs the original WebP as well, keep that file. This conversion writes a new JPEG beside it. It does not replace the source on disk until you decide to delete it.
Questions
Why did my browser save a WebP?
Because the site sent one. Chrome, Edge, and Firefox are happy to keep the bytes they were given. Right-click, Save image as, and the file is often .webp even though it looked like an ordinary photograph. News sites, shops, and search result thumbnails do this because WebP is smaller than JPEG for a similar look.
Will converting to JPG make the picture sharper?
No. If the WebP was saved with lossy compression, the detail is already gone. JPEG cannot reconstruct it. The slider only decides how hard to compress the pixels you still have. Leave it high if the JPEG will be printed or cropped. Lower it for a quick email.
What happens to transparency?
JPEG has no alpha channel. Transparent pixels are drawn over white before the file is encoded. Logos and stickers usually want WebP to PNG instead, so the transparent areas survive. Photographs rarely need that.
Can I convert an animated WebP?
You get a single frame, the one the browser decodes as the image bitmap. The animation is not exported as a video or as a stack of frames. For a still photo saved as WebP, that is the whole file anyway.
Is the file uploaded?
No. FromHEIC decodes the WebP with the browser and encodes the JPEG on a canvas in the tab. Nothing is posted to a server.
Do I need a plugin?
No. Current browsers decode WebP themselves. If a very old browser cannot, the row says the file could not be decoded. There is no plugin to install and no server-side retry.