Which format is used for portable images that support transparency?

The .PNG format is specifically designed to handle images with transparent backgrounds, making it a popular choice for web graphics and design projects that require such features. Unlike other formats, .PNG supports an alpha channel, which allows for varying degrees of transparency. This capability enables smooth edges and the incorporation of images over different backgrounds without having a solid color box around them.

While .JPEG/.JPG is widely used for high-quality photographs, it does not support transparency, instead compressing images in a way that does not retain alpha channels. The .BMP format, although it can handle larger images without any compression artifacts, does not inherently support transparency. The .GIF format can support transparency but is limited to a single transparent color and has a restricted color palette, which may not provide the versatility needed for more complex images. Hence, .PNG stands out as the best option for portable images that need to maintain transparency effectively.