Compare a WebP export without assuming it is better
Define the intended use
Choose a still source image and check whether the receiving application accepts WebP. A compact file is useful only if the destination can use it and its visible detail is suitable. Keep a source master and any required alternative format.
Make a first export
Prepare an output at quality 85 or another setting that suits the image. Read the original and output sizes on the result card. Do not choose a file solely because its extension is WebP; an already efficient source can produce a larger export.
Calculate the size difference
Subtract output bytes from original bytes and divide by original bytes. A change from 500 KB to 350 KB is a 30% reduction. This example explains the formula. Actual results depend on dimensions, content and the browser encoder, and are displayed for each processed image.
Compare appearance and alpha
Inspect text, straight lines, gradients and transparent edges. A transparent source can retain its alpha channel, but this does not mean every visible pixel is unchanged. An opaque source does not become a cutout. Check the file on the background where it will be used.
Keep an alternative
Download the result when both its size and appearance meet the requirement. Retain the original if the result is larger or the destination does not accept WebP. The workflow does not preserve animation or every original metadata field, and the quality control is not a dedicated lossless mode.
Try and verify the workflow
Try a photograph at quality 80, then compare fine details. The best setting depends on the image, and some sources will already be efficiently encoded.
Open webp converter