Choosing the wrong image format costs you page speed, user experience, and bandwidth. Here's a practical guide to the four major formats and when each makes sense. JPEG (JPG) — Still the universal standard Best for: Photographs, complex images with many colors. JPEG uses lossy compression that works well for natural scenes. It's supported everywhere. The downsides: no transparency, no animation, and visible artefacts at very low quality settings. When to use it : Backgroun...