The moment WebP stops being invisible
Most people never notice WebP exists. You right-click an image on a website, save it, and move on — until you try to attach it somewhere that quietly rejects the file, or open it in an older editor that just shows a broken-image icon. That's the exact moment WebP goes from "the format your browser handles automatically" to "a format half your other software has never heard of."
It's not that WebP is broken or unusual — it's genuinely a good format, which is exactly why so many sites switched to it. The problem is purely about the gap between what your browser supports and what everything else on your computer supports.
Why this keeps happening more often now
A few years ago this almost never came up, because WebP was rare outside of Google's own properties. Now it's the default output for a large share of the web — product photos on shopping sites, blog images, social media uploads — so the odds of saving a WebP file without realizing it have gone up considerably. Meanwhile, plenty of everyday software (some older photo editors, certain document tools, some upload forms on other platforms) hasn't caught up.
JPG is the one format that basically never has this problem. It's been the default for photos for decades, which is precisely why converting to it is the fastest fix rather than trying to find WebP support in whatever tool is rejecting your file.
The one thing to watch for: transparency
WebP supports transparent backgrounds the same way PNG does — something JPG simply can't represent at all. If your WebP image has a transparent area (common for logos, icons, or graphics pulled from a website), converting straight to JPG needs somewhere for that transparency to go. A good converter fills it with a background color you choose rather than defaulting to an ugly black block, so check that setting before converting anything with see-through areas.
What you're trading away, and why it's usually fine
WebP is more efficient than JPEG at the same visual quality, so converting almost always makes the file somewhat larger for the same look — that's the real cost of gaining universal compatibility. For a one-off image you need to use in a specific place, that trade is obviously worth it. If you're dealing with dozens of images and file size actually matters (say, for a website you're building), it's worth asking whether you can just keep them as WebP and only convert the handful that genuinely need to go somewhere WebP-unfriendly.