The PNG vs JPG decision comes down to content type. They're optimised for fundamentally different kinds of images, and using the wrong one either wastes bandwidth or degrades quality.
PNG excels at images with sharp edges, flat colours, and text — screenshots, logos, UI elements, diagrams, and illustrations. It uses lossless compression, meaning no data is discarded. It also supports transparency (alpha channels), which makes it essential for logos and overlays. The downside: PNG files of photographs are enormous because lossless compression can't efficiently handle the complexity of natural images.
JPG excels at photographs and natural images — anything with smooth gradients, complex textures, and millions of subtle colour variations. Its lossy compression is specifically designed for this type of content. A photo saved as JPG at quality 85 looks identical to the original at a fraction of the file size.
The quick test: does the image have more than 256 colours and come from a camera? Use JPG. Does it have text, sharp lines, flat colours, or transparency? Use PNG. Is it a screenshot of a photo? This is the edge case — JPG if file size matters, PNG if you need pixel-perfect reproduction.
For modern web development, WebP handles both cases and produces smaller files than either format, but JPG and PNG remain the universal defaults.
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