Guide
Three formats cover almost every image you'll ever handle online. Here's the actual difference — not the technical spec, just what it means for your file.
The oldest and most universally supported of the three. Built for photographs — it compresses smoothly for realistic images with lots of color variation, but it has no concept of transparency, and it's a lossy format, meaning every re-save loses a little more quality.
Use JPG when: you're saving a photo, you need maximum compatibility with older tools or print services, or transparency isn't relevant.
Lossless — nothing is thrown away when you save it — and it supports transparency. The tradeoff is size: PNG files are typically much larger than JPG or WebP for photographic content, since it wasn't designed to compress that kind of detail efficiently.
Use PNG when: you need transparency, you're saving a screenshot or graphic with sharp edges and text, or you're keeping a master copy for further editing.
The newest of the three, and often the best of both worlds — it supports transparency like PNG, but compresses photographic content closer to JPG's efficiency, typically producing files 25–35% smaller than an equivalent-quality JPG. All current major browsers support it.
Use WebP when: the image is headed to a website and load speed matters, or you need transparency in a smaller file than PNG would give you.
Not sure which will actually be smaller for your specific image? Results vary — the safest approach is to try the Image Compressor, which tests the right formats for your image automatically and picks the smallest one that meets your target.