Choose for the actual task

For a web photograph, start by comparing WebP with JPEG. For a diagram, screenshot or logo that needs exact edges, compare PNG with a lossless alternative. WebP can support transparency and both lossy and lossless compression; JPEG does not preserve an alpha channel. Format support is only the first check: a particular converter may export fewer features than the format allows. Keep an untouched original before experimenting.

Resize before chasing a quality setting

An image shown at 800 pixels wide rarely needs a 6,000-pixel export for that same placement. Decide the displayed size and the sharpness required on high-density screens, then resize while preserving the aspect ratio. Cropping changes the composition; resizing changes dimensions. Use a separate larger image when a product page needs zoom. A tiny thumbnail should not be enlarged into the main product photograph.

Compare at the size people will see

Try a moderate quality setting, inspect the export at its intended display size, and compare the actual file sizes. Look closely at lettering, hair, fine fabric and smooth gradients: these reveal compression damage quickly. A quality value of 80 is not a universal visual standard across encoders. Do not promise a fixed percentage reduction; a file that is already efficient may shrink little or even grow.

Check transparency, orientation and animation

Transparent artwork needs an output that retains its alpha channel. When producing JPEG, choose a deliberate background colour rather than accepting accidental black edges. Reopen the saved file and check orientation and colours. A still-image converter may keep only one frame of an animated input, and metadata may be removed during export. Keep the original whenever those properties matter.

Use a repeatable publishing workflow

Prepare the crop, resize once, export two candidate formats and select the smaller acceptable result. Give the file a meaningful name and write alternative text describing the image’s purpose. Check the finished page on mobile as well as desktop. This workflow is an editorial recommendation, not a benchmark of a particular encoder: the useful measure is the result your visitors receive.

Editorial research based on the sources listed below.

developers.google.com · developer.mozilla.org