WebP compression — Input checklist

Worked example

Before compressing a WebP, confirm it is a still image, then note its transparency and how it was encoded.

Picture a blogger who saved banner images from a site and now has a 1600 × 900 WebP at a heavy weight. First check that it is not animated. The tool draws the image onto a canvas, so an animated WebP would come out as one still frame and the motion would be lost. If you need the animation, do not use this step.

Next, think about the history. A WebP saved from another site was almost certainly encoded lossy once already, and compressing it again at a lower quality adds new artefacts to old ones. A lossless WebP, often used for graphics and screenshots, behaves differently, because the browser will re-encode it as lossy at the slider value, trading exact pixels for a smaller file.

Check transparency by viewing the file over a dark and a light background. A cut-out product with soft edges needs a gentler setting than an opaque photo. The tool keeps the alpha channel of WebP, but it only keeps what exists, so a source that was flattened earlier cannot regain transparency.

Do a final check before you press the button: record the dimensions and bytes, and confirm your browser displays the file correctly. An image above 64 million pixels is refused with a message to crop or resize first, and a source that is not JPG, PNG or WebP is exported as PNG, which can be heavier than the file you started with.

WebP still image

WebP still export

Animated WebP files are not kept as animations here; assume the output is a single frame.