Why so much software won't open WebP
WebP is a modern image format that browsers now save and display automatically, which is why you so often end up with one after saving a picture from a web page. The problem appears the moment you try to use it somewhere other than a browser: plenty of desktop photo editors, older phones, document tools and upload forms still do not recognise WebP and simply refuse the file or show nothing.
Converting to JPG solves that in one step, because JPG is the most widely supported image format there is — essentially every program, device and website that handles images at all can read it. You trade WebP's smaller size for compatibility that works everywhere, which is exactly the right trade when something you need to use has rejected your WebP.
It is worth doing the conversion once and keeping the JPG, rather than repeatedly fighting the same compatibility wall. Once you have a JPG copy, it will open in essentially any editor, attach to any email, and upload to any form, so the WebP problem stops recurring every time you need to use the image somewhere new. Converting it once and keeping that JPG copy is almost always far less work than repeatedly hitting the same compatibility wall on every new device or program.
What the conversion costs you
Both WebP and JPG are lossy formats, so converting between them re-encodes the image and technically loses a small amount of quality in the process. In practice, at the default quality this is imperceptible for photographs at normal viewing sizes, and you can raise the quality slider if you are keeping the result for something print-critical.
The one real change is transparency. WebP can hold an alpha channel; JPG cannot. If your WebP has transparent areas, they will be filled with white when it becomes a JPG. That is fine for most photos and screenshots, but if you specifically need the transparency, convert the WebP to PNG instead, which keeps it intact.
Converted privately, in batches
The conversion happens inside your browser using its native image decoding, so your WebP files are never uploaded anywhere. That is genuinely useful when the images are personal — photos saved from a chat, a screenshot of something private — because nothing you convert is transmitted, stored or seen by any server.
You can also drop a whole set of WebP files at once. Each is converted to a JPG in turn, the size of each result is shown, and you can download them individually or as a single ZIP. Because it is all local, there is no upload wait and no limit imposed by a service — only what your own device can comfortably process.
Batch conversion without the wait
Handling one file is easy anywhere; the value of a local tool shows when you have a folder of them. Drop a whole set of WebP images and each is converted to JPG in sequence, with the resulting size shown per file so you can see what you are getting before you download anything.
You can then take each JPG individually or download the whole set as a single ZIP. There is no upload queue to sit through and no per-file cap imposed by a server, because the work happens on your own machine — the only real limit is how many images your device can comfortably hold in memory at once.