Optimize tools

Most images on the web are several times larger than they need to be, usually because they came straight off a camera or a design tool at full quality. Compression re-encodes the file at a lower quality setting, and the useful range is wide — a photograph often survives a large reduction with no difference you can see at normal viewing size.

The trade-off depends on the content. Photographs, with their gradual tonal shifts, compress extremely well. Screenshots, line art, and anything with hard edges or flat colour do not — they show artefacts around the edges first. If a compressed image looks soft or blocky in those areas, ease the quality back up or convert to a format better suited to flat colour.