Level: Basic
Serving a single, large image to every device wastes bandwidth on smaller screens that don't need that much resolution, hurting mobile load time specifically.
Different Devices Genuinely Need Different Image Sizes
A full desktop-resolution image is unnecessarily large for a small mobile screen, where a smaller file serves the same visual purpose.
Responsive Image Techniques Let the Browser Choose
Modern responsive image approaches let a browser select the appropriately sized version of an image based on the actual device and screen, rather than forcing one size on everyone.
This Is Especially Important on Image-Heavy Pages
A page with many images compounds the impact of oversized files, making responsive image handling especially valuable wherever visual content is dense.
Next step: Use the Page Size Checker to check how much of your page weight on mobile is coming from images that could be served at a smaller, more appropriate size.