There is no universal WebP percentage that works for every image. A portrait, a cloudy sky, a screenshot and a product photo fail in different places. The practical target is the smallest file that still survives the details your viewer will notice.
Lossy compression can simplify texture and create smearing around fine high-contrast detail. Look at eyelashes, hair strands, fabric weave, grass, branches and small product lettering before accepting a lower setting.
Inspect the exported file at the size it will actually be shown. A defect that is obvious at 300% zoom may not matter in a 400-pixel card, while the same defect can be distracting in a large product image.
Look for ringing, colored fringes and mushy small lettering. Graphic content often needs a more conservative lossy setting—or a lossless route.
Watch for waxy skin, smeared strands and texture that suddenly becomes patchy. Faces attract attention, so modest compression defects can feel more obvious.
Large smooth areas can reveal banding or block structure. A file can look sharp around objects while the sky quietly falls apart.
A sky, studio backdrop or shadow transition may show banding or contour-like steps as compression becomes more aggressive. These flaws are easy to miss when you only inspect the center subject.
Open the result on a normal display at normal brightness. Do not make the final decision from a tiny editor thumbnail.
Create a clean reference export. This gives you something to compare against instead of judging each file in isolation.
Try a few separated settings rather than exporting every single percentage. Once you notice damage, move back upward and narrow the range.
If dropping from one setting to another saves only a tiny amount but visibly harms the image, the lower setting has no practical advantage.
WebP supports both lossy and lossless compression. In lossy mode, stronger compression trades away image information for a smaller file. MDN recommends compressing as much as practical while keeping acceptable visual quality; the acceptable point depends on the content and use case.
MDN’s format guide documents WebP’s lossy/lossless modes and alpha support.
