To optimize images for various screen sizes and devices, website owners should employ responsive design techniques. This involves using CSS to serve different image sizes based on the device's screen dimensions. Utilizing HTML's srcset attribute allows browsers to select the appropriate image resolution, improving load times and appearance across devices. Additionally, compressing images and using modern formats like WebP can offer high-quality visuals with reduced file sizes, ensuring faster loading and a consistent user experience on desktops, mobile phones, and tablets.