JPEG

The other popular file format used on the web is JPEG (named after the Joint Photographic Expert Group that designed this format). In the early web years, JPEG images were not displayed in the page but were displayed in a separate window, using an external "helper" application. But most all web browsers these days support JPEG images.

JPEG compression is very effective for photographic images where the colors can vary spatially over short distances ("grainy" images). JPEG offers some dramatic compression in filesize, sometimes by a factor of 10 (e.g. a 1500 kb file reduced to 150 kb), which may be at a trade-off for some image quality. JPEG images do not have the ability to be transparent.