Pick the right format
WebP for photographs, SVG for logos and icons, PNG only where lossless raster is genuinely needed. Converting a photographic PNG to WebP routinely saves ninety per cent.
Resize before you compress
A 4000px photograph displayed at 800px wastes most of its bytes. Resize to the largest size actually displayed, then compress.
Let the browser help
Add width and height so layout does not shift, use loading="lazy" below the fold, and serve responsive sizes with srcset where it matters.
