Level: Basic
Image optimization is one of the highest-leverage, most design-relevant performance improvements available, since images are often the largest assets on a page.
Choose the Right File Format for Each Use Case
Different image formats offer different tradeoffs between quality and file size, and choosing appropriately for each specific image can meaningfully reduce overall page weight.
Compress Thoughtfully, Not Just Maximally
Aggressive compression can introduce visible quality loss; the goal is finding the point of genuinely diminishing visual returns, not just the smallest possible file size.
Resize Images to Their Actual Display Size
Serving an image larger than its actual displayed dimensions wastes bandwidth without providing any visible quality benefit.
Next step: Use the Page Size Checker to check exactly how much of your page weight is currently coming from images before deciding where to optimize.