JPEG to WebP — Verify the result

Worked example

Compare the .webp with the JPEG on byte size, pixel dimensions and gradients at 100 percent, and do not assume it is smaller.

The file is named after the original plus -convert, so lake.jpg becomes lake-convert.webp. Write down both byte counts rather than trusting the summary. Suppose a 480 KB JPEG gives a 310 KB WebP: that is a real saving of about a third. If the WebP is 520 KB, the JPEG was already well compressed and the conversion did not help for that picture.

Dimensions must be the same, for example 1600 × 1067 px both before and after, because the converter does not resize. If they differ, you opened the wrong file or an earlier resize step changed it.

Then look at the places where lossy formats fail: a sky gradient, a shadow fading to black, smooth skin. Zoom to 100 percent, then 200 percent, and compare with the JPEG in another window. Banding, which appears as visible steps in a gradient, is the most common difference.

Finally open the WebP in the browser you expect your audience to use and, if possible, in the software that will receive it. A format that displays in a browser can still be refused by an older editor, so confirm it opens where it will be used.

Keep a note of the byte counts for two or three test files; they give you a realistic expectation for the rest of the catalogue.

JPEG photograph

WebP photograph

Compare actual byte counts, because WebP is not guaranteed to be smaller than the JPEG you started with.